From 67104dd615c82de64839de60418110211438f574 Mon Sep 17 00:00:00 2001
From: Koen De Groote <kdg.private@gmail.com>
Date: Mon, 10 Jun 2019 18:07:43 +0200
Subject: [PATCH] LUCENE-8847: Code Cleanup: Rewrite StringBuilder.append with
 concatted strings (#707)

This specific commit affects all points in the casebase where the argument of a StringBuilder.append() call is itself a regular String concatenation.
This defeats the purpose of using StringBuilder and also introduces an extra alloction.
These changes should avoid that.

ant tests have run, succeeded on local machine.

Removing test files from the changes.

Another suggested rework.
---
 lucene/CHANGES.txt                            |  4 ++
 .../PartOfSpeechAttributeImpl.java            |  2 +-
 .../analysis/cn/smart/hhmm/BiSegGraph.java    |  2 +-
 .../analysis/cn/smart/hhmm/SegGraph.java      |  2 +-
 .../src/java/org/egothor/stemmer/Diff.java    | 14 +++---
 .../byTask/feeds/AbstractQueryMaker.java      |  2 +-
 .../byTask/feeds/ContentItemsSource.java      |  8 +--
 .../benchmark/byTask/tasks/TaskSequence.java  |  6 +--
 .../quality/trec/TrecTopicsReader.java        |  4 +-
 .../lucene/document/LatLonPointSortField.java |  2 +-
 .../org/apache/lucene/index/MergePolicy.java  |  2 +-
 .../org/apache/lucene/index/MultiBits.java    |  8 +--
 .../java/org/apache/lucene/index/Terms.java   | 10 ++--
 .../org/apache/lucene/util/UnicodeUtil.java   |  2 +-
 .../lucene/util/automaton/Automaton.java      |  4 +-
 .../lucene/util/automaton/RunAutomaton.java   |  2 +-
 .../java/org/apache/lucene/util/fst/FST.java  | 10 ++--
 .../org/apache/lucene/facet/FacetResult.java  |  2 +-
 .../lucene/facet/range/LongRangeCounter.java  |  4 +-
 .../directory/DirectoryTaxonomyReader.java    |  6 +--
 .../lucene/index/memory/MemoryIndex.java      | 16 +++---
 .../lucene/misc/SweetSpotSimilarity.java      |  3 +-
 .../queryparser/classic/ParseException.java   |  2 +-
 .../queryparser/classic/TokenMgrError.java    |  2 +-
 .../flexible/core/nodes/AnyQueryNode.java     |  3 +-
 .../core/nodes/ProximityQueryNode.java        |  3 +-
 .../standard/parser/ParseException.java       |  2 +-
 .../standard/parser/TokenMgrError.java        |  2 +-
 .../surround/parser/ParseException.java       |  2 +-
 .../surround/parser/TokenMgrError.java        |  2 +-
 .../lucene/document/LatLonShapeLineQuery.java |  2 +-
 .../document/LatLonShapePolygonQuery.java     |  2 +-
 .../org/apache/lucene/geo/Tessellator.java    |  4 +-
 .../lucene/search/TermAutomatonQuery.java     |  4 +-
 .../prefix/NumberRangePrefixTreeStrategy.java |  4 +-
 .../prefix/RecursivePrefixTreeStrategy.java   |  2 +-
 .../apache/lucene/spatial3d/Geo3DPoint.java   |  6 +--
 .../spatial3d/Geo3DPointOutsideSortField.java |  2 +-
 .../lucene/spatial3d/Geo3DPointSortField.java |  2 +-
 .../jaspell/JaspellTernarySearchTrie.java     |  4 +-
 .../lucene/geo/BaseGeoPointTestCase.java      | 38 +++++++-------
 .../org/apache/lucene/geo/EarthDebugger.java  | 50 +++++++++----------
 .../org/apache/lucene/geo/GeoTestUtil.java    |  8 +--
 .../search/BaseRangeFieldQueryTestCase.java   | 14 +++---
 .../apache/lucene/util/LuceneTestCase.java    |  4 +-
 .../lucene/validation/LicenseCheckTask.java   |  4 +-
 .../extraction/XLSXResponseWriter.java        |  6 +--
 .../autoscaling/sim/SimCloudManager.java      | 28 +++++------
 .../java/org/apache/solr/core/PluginInfo.java | 10 ++--
 .../admin/SegmentsInfoRequestHandler.java     |  4 +-
 .../apache/solr/handler/export/SortDoc.java   |  4 +-
 .../apache/solr/parser/ParseException.java    |  2 +-
 .../org/apache/solr/parser/TokenMgrError.java |  2 +-
 .../solr/schema/SimplePreAnalyzedParser.java  | 12 ++---
 .../org/apache/solr/search/QueryParsing.java  |  7 ++-
 .../apache/solr/search/join/GraphQuery.java   | 12 ++---
 .../solr/update/SolrCmdDistributor.java       |  2 +-
 .../apache/solr/update/SplitIndexCommand.java | 14 +++---
 .../org/apache/solr/util/SimplePostTool.java  |  2 +-
 .../org/apache/solr/util/SolrLogLayout.java   | 10 ++--
 .../org/apache/solr/util/SolrPluginUtils.java |  2 +-
 .../client/solrj/io/stream/Facet2DStream.java | 16 +++---
 .../client/solrj/io/stream/FacetStream.java   | 10 ++--
 .../client/solrj/io/stream/KnnStream.java     |  2 +-
 .../solrj/io/stream/TimeSeriesStream.java     | 10 ++--
 .../client/solrj/request/UpdateRequest.java   |  6 +--
 .../solr/common/cloud/ClusterState.java       |  6 +--
 .../solr/common/cloud/SolrZkClient.java       |  9 ++--
 .../apache/solr/common/util/ExecutorUtil.java |  2 +-
 .../cloud/AbstractFullDistribZkTestBase.java  |  2 +-
 .../org/apache/solr/cloud/ChaosMonkey.java    |  2 +-
 71 files changed, 231 insertions(+), 234 deletions(-)

diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 1c818bdb695..369340ccb00 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -93,6 +93,10 @@ Test Framework
 * LUCENE-8825: CheckHits now display the shard index in case of mismatch
   between top hits. (Atri Sharma via Adrien Grand)
 
+Other
+
+* LUCENE-8847: Code Cleanup: Remove StringBuilder.append with concatted strings
+
 ======================= Lucene 8.1.1 =======================
 (No Changes)
 
diff --git a/lucene/analysis/nori/src/java/org/apache/lucene/analysis/ko/tokenattributes/PartOfSpeechAttributeImpl.java b/lucene/analysis/nori/src/java/org/apache/lucene/analysis/ko/tokenattributes/PartOfSpeechAttributeImpl.java
index fbd637f92b2..14a40b651cc 100644
--- a/lucene/analysis/nori/src/java/org/apache/lucene/analysis/ko/tokenattributes/PartOfSpeechAttributeImpl.java
+++ b/lucene/analysis/nori/src/java/org/apache/lucene/analysis/ko/tokenattributes/PartOfSpeechAttributeImpl.java
@@ -80,7 +80,7 @@ public class PartOfSpeechAttributeImpl extends AttributeImpl implements PartOfSp
       if (builder.length() > 0) {
         builder.append("+");
       }
-      builder.append(morpheme.surfaceForm + "/" + morpheme.posTag.name() + "(" + morpheme.posTag.description() + ")");
+      builder.append(morpheme.surfaceForm).append('/').append(morpheme.posTag.name()).append('(').append(morpheme.posTag.description()).append(')');
     }
     return builder.toString();
   }
diff --git a/lucene/analysis/smartcn/src/java/org/apache/lucene/analysis/cn/smart/hhmm/BiSegGraph.java b/lucene/analysis/smartcn/src/java/org/apache/lucene/analysis/cn/smart/hhmm/BiSegGraph.java
index 33074983543..2c92b083fa3 100644
--- a/lucene/analysis/smartcn/src/java/org/apache/lucene/analysis/cn/smart/hhmm/BiSegGraph.java
+++ b/lucene/analysis/smartcn/src/java/org/apache/lucene/analysis/cn/smart/hhmm/BiSegGraph.java
@@ -222,7 +222,7 @@ class BiSegGraph {
     Collection<ArrayList<SegTokenPair>>  values = tokenPairListTable.values();
     for (ArrayList<SegTokenPair> segList : values) {
       for (SegTokenPair pair : segList) {
-        sb.append(pair + "\n");
+        sb.append(pair).append("\n");
       }
     }
     return sb.toString();
diff --git a/lucene/analysis/smartcn/src/java/org/apache/lucene/analysis/cn/smart/hhmm/SegGraph.java b/lucene/analysis/smartcn/src/java/org/apache/lucene/analysis/cn/smart/hhmm/SegGraph.java
index a6f38b31759..e01438cf0d7 100644
--- a/lucene/analysis/smartcn/src/java/org/apache/lucene/analysis/cn/smart/hhmm/SegGraph.java
+++ b/lucene/analysis/smartcn/src/java/org/apache/lucene/analysis/cn/smart/hhmm/SegGraph.java
@@ -136,7 +136,7 @@ class SegGraph {
     List<SegToken> tokenList = this.toTokenList();
     StringBuilder sb = new StringBuilder();
     for (SegToken t : tokenList) {
-      sb.append(t + "\n");
+      sb.append(t).append("\n");
     }
     return sb.toString();
   }
diff --git a/lucene/analysis/stempel/src/java/org/egothor/stemmer/Diff.java b/lucene/analysis/stempel/src/java/org/egothor/stemmer/Diff.java
index fe50449b7d4..da720fcfc0e 100644
--- a/lucene/analysis/stempel/src/java/org/egothor/stemmer/Diff.java
+++ b/lucene/analysis/stempel/src/java/org/egothor/stemmer/Diff.java
@@ -239,7 +239,7 @@ public class Diff {
       switch (way[x][y]) {
         case X:
           if (equals != base) {
-            result.append("-" + (equals));
+            result.append('-').append(equals);
             equals = base;
           }
           deletes++;
@@ -248,11 +248,11 @@ public class Diff {
         // delete
         case Y:
           if (deletes != base) {
-            result.append("D" + (deletes));
+            result.append('D').append(deletes);
             deletes = base;
           }
           if (equals != base) {
-            result.append("-" + (equals));
+            result.append('-').append(equals);
             equals = base;
           }
           result.append('I');
@@ -261,11 +261,11 @@ public class Diff {
         // insert
         case R:
           if (deletes != base) {
-            result.append("D" + (deletes));
+            result.append('D').append(deletes);
             deletes = base;
           }
           if (equals != base) {
-            result.append("-" + (equals));
+            result.append('-').append(equals);
             equals = base;
           }
           result.append('R');
@@ -275,7 +275,7 @@ public class Diff {
         // replace
         case D:
           if (deletes != base) {
-            result.append("D" + (deletes));
+            result.append('D').append(deletes);
             deletes = base;
           }
           equals++;
@@ -286,7 +286,7 @@ public class Diff {
       }
     }
     if (deletes != base) {
-      result.append("D" + (deletes));
+      result.append('D').append(deletes);
       deletes = base;
     }
     
diff --git a/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/feeds/AbstractQueryMaker.java b/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/feeds/AbstractQueryMaker.java
index b40f4a91d46..a56f9786080 100644
--- a/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/feeds/AbstractQueryMaker.java
+++ b/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/feeds/AbstractQueryMaker.java
@@ -50,7 +50,7 @@ public abstract class AbstractQueryMaker implements QueryMaker {
     StringBuilder sb = new StringBuilder();
     if (queries != null) {
       for (int i = 0; i < queries.length; i++) {
-        sb.append(i+". "+ queries[i].getClass().getSimpleName()+" - "+queries[i].toString());
+        sb.append(i).append(". ").append(queries[i].getClass().getSimpleName()).append(" - ").append(queries[i].toString());
         sb.append(newline);
       }
     }
diff --git a/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/feeds/ContentItemsSource.java b/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/feeds/ContentItemsSource.java
index 7e15083a27e..385edc8f2f6 100644
--- a/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/feeds/ContentItemsSource.java
+++ b/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/feeds/ContentItemsSource.java
@@ -159,19 +159,19 @@ public abstract class ContentItemsSource implements Closeable {
     int nut = getTotalItemsCount();
     if (nut > lastPrintedNumUniqueTexts) {
       print = true;
-      sb.append("total count of "+itemsName+": ").append(Format.format(0,nut,col)).append(newline);
+      sb.append("total count of ").append(itemsName).append(": ").append(Format.format(0,nut,col)).append(newline);
       lastPrintedNumUniqueTexts = nut;
     }
     long nub = getTotalBytesCount();
     if (nub > lastPrintedNumUniqueBytes) {
       print = true;
-      sb.append("total bytes of "+itemsName+": ").append(Format.format(0,nub,col)).append(newline);
+      sb.append("total bytes of ").append(itemsName).append(": ").append(Format.format(0,nub,col)).append(newline);
       lastPrintedNumUniqueBytes = nub;
     }
     if (getItemsCount() > 0) {
       print = true;
-      sb.append("num "+itemsName+" added since last inputs reset:   ").append(Format.format(0,getItemsCount(),col)).append(newline);
-      sb.append("total bytes added for "+itemsName+" since last inputs reset: ").append(Format.format(0,getBytesCount(),col)).append(newline);
+      sb.append("num ").append(itemsName).append(" added since last inputs reset:   ").append(Format.format(0,getItemsCount(),col)).append(newline);
+      sb.append("total bytes added for ").append(itemsName).append(" since last inputs reset: ").append(Format.format(0,getBytesCount(),col)).append(newline);
     }
     if (print) {
       System.out.println(sb.append(newline).toString());
diff --git a/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/TaskSequence.java b/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/TaskSequence.java
index c57845da621..4b2f94c2b2b 100644
--- a/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/TaskSequence.java
+++ b/lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/TaskSequence.java
@@ -436,14 +436,14 @@ public class TaskSequence extends PerfTask {
     sb.append(padd);
     sb.append(!letChildReport ? ">" : (parallel ? "]" : "}"));
     if (fixedTime) {
-      sb.append(" " + NumberFormat.getNumberInstance(Locale.ROOT).format(runTimeSec) + "s");
+      sb.append(' ').append(NumberFormat.getNumberInstance(Locale.ROOT).format(runTimeSec)).append('s');
     } else if (repetitions>1) {
-      sb.append(" * " + repetitions);
+      sb.append(" * ").append(repetitions);
     } else if (repetitions==REPEAT_EXHAUST) {
       sb.append(" * EXHAUST");
     }
     if (rate>0) {
-      sb.append(",  rate: " + rate+"/"+(perMin?"min":"sec"));
+      sb.append(",  rate: ").append(rate).append('/').append(perMin ? "min" : "sec");
     }
     if (getRunInBackground()) {
       sb.append(" &");
diff --git a/lucene/benchmark/src/java/org/apache/lucene/benchmark/quality/trec/TrecTopicsReader.java b/lucene/benchmark/src/java/org/apache/lucene/benchmark/quality/trec/TrecTopicsReader.java
index 8c478ab3c0b..99e628ae15c 100644
--- a/lucene/benchmark/src/java/org/apache/lucene/benchmark/quality/trec/TrecTopicsReader.java
+++ b/lucene/benchmark/src/java/org/apache/lucene/benchmark/quality/trec/TrecTopicsReader.java
@@ -122,13 +122,13 @@ public class TrecTopicsReader {
       }
       if (line.startsWith(prefix)) {
         if (collectMatchLine) {
-          sb.append(sep+line);
+          sb.append(sep).append(line);
           sep = newline;
         }
         break;
       }
       if (collectAll) {
-        sb.append(sep+line);
+        sb.append(sep).append(line);
         sep = newline;
       }
     }
diff --git a/lucene/core/src/java/org/apache/lucene/document/LatLonPointSortField.java b/lucene/core/src/java/org/apache/lucene/document/LatLonPointSortField.java
index 10e72cc2e98..8d6f652ed83 100644
--- a/lucene/core/src/java/org/apache/lucene/document/LatLonPointSortField.java
+++ b/lucene/core/src/java/org/apache/lucene/document/LatLonPointSortField.java
@@ -92,7 +92,7 @@ final class LatLonPointSortField extends SortField {
     builder.append(" longitude=");
     builder.append(longitude);
     if (Double.POSITIVE_INFINITY != getMissingValue()) {
-      builder.append(" missingValue=" + getMissingValue());
+      builder.append(" missingValue=").append(getMissingValue());
     }
     builder.append('>');
     return builder.toString();
diff --git a/lucene/core/src/java/org/apache/lucene/index/MergePolicy.java b/lucene/core/src/java/org/apache/lucene/index/MergePolicy.java
index d552d74ba49..dc8a1d3d885 100644
--- a/lucene/core/src/java/org/apache/lucene/index/MergePolicy.java
+++ b/lucene/core/src/java/org/apache/lucene/index/MergePolicy.java
@@ -303,7 +303,7 @@ public abstract class MergePolicy {
         b.append(" into ").append(info.info.name);
       }
       if (maxNumSegments != -1) {
-        b.append(" [maxNumSegments=" + maxNumSegments + "]");
+        b.append(" [maxNumSegments=").append(maxNumSegments).append(']');
       }
       if (isAborted()) {
         b.append(" [ABORTED]");
diff --git a/lucene/core/src/java/org/apache/lucene/index/MultiBits.java b/lucene/core/src/java/org/apache/lucene/index/MultiBits.java
index b1f5f51d532..27e7e0cb8cf 100644
--- a/lucene/core/src/java/org/apache/lucene/index/MultiBits.java
+++ b/lucene/core/src/java/org/apache/lucene/index/MultiBits.java
@@ -98,18 +98,18 @@ public final class MultiBits implements Bits {
   @Override
   public String toString() {
     StringBuilder b = new StringBuilder();
-    b.append(subs.length + " subs: ");
+    b.append(subs.length).append(" subs: ");
     for(int i=0;i<subs.length;i++) {
       if (i != 0) {
         b.append("; ");
       }
       if (subs[i] == null) {
-        b.append("s=" + starts[i] + " l=null");
+        b.append("s=").append(starts[i]).append(" l=null");
       } else {
-        b.append("s=" + starts[i] + " l=" + subs[i].length() + " b=" + subs[i]);
+        b.append("s=").append(starts[i]).append(" l=").append(subs[i].length()).append(" b=").append(subs[i]);
       }
     }
-    b.append(" end=" + starts[subs.length]);
+    b.append(" end=").append(starts[subs.length]);
     return b.toString();
   }
 
diff --git a/lucene/core/src/java/org/apache/lucene/index/Terms.java b/lucene/core/src/java/org/apache/lucene/index/Terms.java
index dabb8f7cdeb..08605a56dc6 100644
--- a/lucene/core/src/java/org/apache/lucene/index/Terms.java
+++ b/lucene/core/src/java/org/apache/lucene/index/Terms.java
@@ -209,11 +209,11 @@ public abstract class Terms {
    */
   public Object getStats() throws IOException {
     StringBuilder sb = new StringBuilder();
-    sb.append("impl=" + getClass().getSimpleName());
-    sb.append(",size=" + size());
-    sb.append(",docCount=" + getDocCount());
-    sb.append(",sumTotalTermFreq=" + getSumTotalTermFreq());
-    sb.append(",sumDocFreq=" + getSumDocFreq());
+    sb.append("impl=").append(getClass().getSimpleName());
+    sb.append(",size=").append(size());
+    sb.append(",docCount=").append(getDocCount());
+    sb.append(",sumTotalTermFreq=").append(getSumTotalTermFreq());
+    sb.append(",sumDocFreq=").append(getSumDocFreq());
     return sb.toString();
   }
 }
diff --git a/lucene/core/src/java/org/apache/lucene/util/UnicodeUtil.java b/lucene/core/src/java/org/apache/lucene/util/UnicodeUtil.java
index 20e6249f2a3..ddb883b42a0 100644
--- a/lucene/core/src/java/org/apache/lucene/util/UnicodeUtil.java
+++ b/lucene/core/src/java/org/apache/lucene/util/UnicodeUtil.java
@@ -569,7 +569,7 @@ public final class UnicodeUtil {
           }
         }
         
-        sb.append("0x" + Integer.toHexString(ch));
+        sb.append("0x").append(Integer.toHexString(ch));
       }
     }
     return sb.toString();
diff --git a/lucene/core/src/java/org/apache/lucene/util/automaton/Automaton.java b/lucene/core/src/java/org/apache/lucene/util/automaton/Automaton.java
index 807ef8f4958..3bfd04fcc27 100644
--- a/lucene/core/src/java/org/apache/lucene/util/automaton/Automaton.java
+++ b/lucene/core/src/java/org/apache/lucene/util/automaton/Automaton.java
@@ -589,9 +589,9 @@ public class Automaton implements Accountable {
       b.append("  ");
       b.append(state);
       if (isAccept(state)) {
-        b.append(" [shape=doublecircle,label=\"" + state + "\"]\n");
+        b.append(" [shape=doublecircle,label=\"").append(state).append("\"]\n");
       } else {
-        b.append(" [shape=circle,label=\"" + state + "\"]\n");
+        b.append(" [shape=circle,label=\"").append(state).append("\"]\n");
       }
       int numTransitions = initTransition(state, t);
       //System.out.println("toDot: state " + state + " has " + numTransitions + " transitions; t.nextTrans=" + t.transitionUpto);
diff --git a/lucene/core/src/java/org/apache/lucene/util/automaton/RunAutomaton.java b/lucene/core/src/java/org/apache/lucene/util/automaton/RunAutomaton.java
index 4f539260450..0b1b71f2d55 100644
--- a/lucene/core/src/java/org/apache/lucene/util/automaton/RunAutomaton.java
+++ b/lucene/core/src/java/org/apache/lucene/util/automaton/RunAutomaton.java
@@ -103,7 +103,7 @@ public abstract class RunAutomaton {
     StringBuilder b = new StringBuilder();
     b.append("initial state: 0\n");
     for (int i = 0; i < size; i++) {
-      b.append("state " + i);
+      b.append("state ").append(i);
       if (accept[i]) b.append(" [accept]:\n");
       else b.append(" [reject]:\n");
       for (int j = 0; j < points.length; j++) {
diff --git a/lucene/core/src/java/org/apache/lucene/util/fst/FST.java b/lucene/core/src/java/org/apache/lucene/util/fst/FST.java
index d713797d11a..c13323fa6a9 100644
--- a/lucene/core/src/java/org/apache/lucene/util/fst/FST.java
+++ b/lucene/core/src/java/org/apache/lucene/util/fst/FST.java
@@ -208,8 +208,8 @@ public final class FST<T> implements Accountable {
     @Override
     public String toString() {
       StringBuilder b = new StringBuilder();
-      b.append(" target=" + target);
-      b.append(" label=0x" + Integer.toHexString(label));
+      b.append(" target=").append(target);
+      b.append(" label=0x").append(Integer.toHexString(label));
       if (flag(BIT_FINAL_ARC)) {
         b.append(" final");
       }
@@ -223,13 +223,13 @@ public final class FST<T> implements Accountable {
         b.append(" stop");
       }
       if (flag(BIT_ARC_HAS_OUTPUT)) {
-        b.append(" output=" + output);
+        b.append(" output=").append(output);
       }
       if (flag(BIT_ARC_HAS_FINAL_OUTPUT)) {
-        b.append(" nextFinalOutput=" + nextFinalOutput);
+        b.append(" nextFinalOutput=").append(nextFinalOutput);
       }
       if (bytesPerArc != 0) {
-        b.append(" arcArray(idx=" + arcIdx + " of " + numArcs + ")");
+        b.append(" arcArray(idx=").append(arcIdx).append(" of ").append(numArcs).append(")");
       }
       return b.toString();
     }
diff --git a/lucene/facet/src/java/org/apache/lucene/facet/FacetResult.java b/lucene/facet/src/java/org/apache/lucene/facet/FacetResult.java
index 7635364337a..5ca221b809c 100644
--- a/lucene/facet/src/java/org/apache/lucene/facet/FacetResult.java
+++ b/lucene/facet/src/java/org/apache/lucene/facet/FacetResult.java
@@ -60,7 +60,7 @@ public final class FacetResult {
     sb.append(childCount);
     sb.append('\n');
     for(LabelAndValue labelValue : labelValues) {
-      sb.append("  " + labelValue + "\n");
+      sb.append("  ").append(labelValue).append("\n");
     }
     return sb.toString();
   }
diff --git a/lucene/facet/src/java/org/apache/lucene/facet/range/LongRangeCounter.java b/lucene/facet/src/java/org/apache/lucene/facet/range/LongRangeCounter.java
index 5c625f08867..855f6ec09b4 100644
--- a/lucene/facet/src/java/org/apache/lucene/facet/range/LongRangeCounter.java
+++ b/lucene/facet/src/java/org/apache/lucene/facet/range/LongRangeCounter.java
@@ -295,9 +295,9 @@ final class LongRangeCounter {
       indent(sb, depth);
       if (left == null) {
         assert right == null;
-        sb.append("leaf: " + start + " to " + end);
+        sb.append("leaf: ").append(start).append(" to ").append(end);
       } else {
-        sb.append("node: " + start + " to " + end);
+        sb.append("node: ").append(start).append(" to ").append(end);
       }
       if (outputs != null) {
         sb.append(" outputs=");
diff --git a/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/DirectoryTaxonomyReader.java b/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/DirectoryTaxonomyReader.java
index c97325cf44d..bcc4c6d5189 100644
--- a/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/DirectoryTaxonomyReader.java
+++ b/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/DirectoryTaxonomyReader.java
@@ -412,14 +412,14 @@ public class DirectoryTaxonomyReader extends TaxonomyReader implements Accountab
       try {
         FacetLabel category = this.getPath(i);
         if (category == null) {
-          sb.append(i + ": NULL!! \n");
+          sb.append(i).append(": NULL!! \n");
           continue;
         } 
         if (category.length == 0) {
-          sb.append(i + ": EMPTY STRING!! \n");
+          sb.append(i).append(": EMPTY STRING!! \n");
           continue;
         }
-        sb.append(i +": "+category.toString()+"\n");
+        sb.append(i).append(": ").append(category.toString()).append("\n");
       } catch (IOException e) {
         if (log.isLoggable(Level.FINEST)) {
           log.log(Level.FINEST, e.getMessage(), e);
diff --git a/lucene/memory/src/java/org/apache/lucene/index/memory/MemoryIndex.java b/lucene/memory/src/java/org/apache/lucene/index/memory/MemoryIndex.java
index b061d51093a..ca9ccd75fa8 100644
--- a/lucene/memory/src/java/org/apache/lucene/index/memory/MemoryIndex.java
+++ b/lucene/memory/src/java/org/apache/lucene/index/memory/MemoryIndex.java
@@ -728,7 +728,7 @@ public class MemoryIndex {
       String fieldName = entry.getKey();
       Info info = entry.getValue();
       info.sortTerms();
-      result.append(fieldName + ":\n");
+      result.append(fieldName).append(":\n");
       SliceByteStartArray sliceArray = info.sliceArray;
       int numPositions = 0;
       SliceReader postingsReader = new SliceReader(intBlockPool);
@@ -736,7 +736,7 @@ public class MemoryIndex {
         int ord = info.sortedTerms[j];
         info.terms.get(ord, spare);
         int freq = sliceArray.freq[ord];
-        result.append("\t'" + spare + "':" + freq + ":");
+        result.append("\t'").append(spare).append("':").append(freq).append(':');
         postingsReader.reset(sliceArray.start[ord], sliceArray.end[ord]);
         result.append(" [");
         final int iters = storeOffsets ? 3 : 1;
@@ -752,7 +752,7 @@ public class MemoryIndex {
           if (storePayloads) {
             int payloadIndex = postingsReader.readInt();
             if (payloadIndex != -1) {
-                result.append(", " + payloadsBytesRefs.get(payloadBuilder, payloadIndex));
+                result.append(", ").append(payloadsBytesRefs.get(payloadBuilder, payloadIndex));
             }
           }
           result.append(")");
@@ -767,16 +767,16 @@ public class MemoryIndex {
         numPositions += freq;
       }
 
-      result.append("\tterms=" + info.terms.size());
-      result.append(", positions=" + numPositions);
+      result.append("\tterms=").append(info.terms.size());
+      result.append(", positions=").append(numPositions);
       result.append("\n");
       sumPositions += numPositions;
       sumTerms += info.terms.size();
     }
     
-    result.append("\nfields=" + fields.size());
-    result.append(", terms=" + sumTerms);
-    result.append(", positions=" + sumPositions);
+    result.append("\nfields=").append(fields.size());
+    result.append(", terms=").append(sumTerms);
+    result.append(", positions=").append(sumPositions);
     return result.toString();
   }
   
diff --git a/lucene/misc/src/java/org/apache/lucene/misc/SweetSpotSimilarity.java b/lucene/misc/src/java/org/apache/lucene/misc/SweetSpotSimilarity.java
index 537322793ce..9287a750ef4 100644
--- a/lucene/misc/src/java/org/apache/lucene/misc/SweetSpotSimilarity.java
+++ b/lucene/misc/src/java/org/apache/lucene/misc/SweetSpotSimilarity.java
@@ -207,8 +207,7 @@ public class SweetSpotSimilarity extends ClassicSimilarity {
   public String toString() {
     StringBuilder sb = new StringBuilder();
     sb.append("SweetSpotSimilarity")
-        .append("(")
-        .append("ln_min="+ln_min+", ")
+        .append('(').append("ln_min=").append(ln_min).append(", ")
         .append("ln_max=").append(ln_max).append(", ")
         .append("ln_steep=").append(ln_steep).append(", ")
         .append("tf_base=").append(tf_base).append(", ")
diff --git a/lucene/queryparser/src/java/org/apache/lucene/queryparser/classic/ParseException.java b/lucene/queryparser/src/java/org/apache/lucene/queryparser/classic/ParseException.java
index 3c02be3f004..fe20c105483 100644
--- a/lucene/queryparser/src/java/org/apache/lucene/queryparser/classic/ParseException.java
+++ b/lucene/queryparser/src/java/org/apache/lucene/queryparser/classic/ParseException.java
@@ -173,7 +173,7 @@ public class ParseException extends Exception {
            default:
               if ((ch = str.charAt(i)) < 0x20 || ch > 0x7e) {
                  String s = "0000" + Integer.toString(ch, 16);
-                 retval.append("\\u" + s.substring(s.length() - 4, s.length()));
+                 retval.append("\\u").append(s.substring(s.length() - 4, s.length()));
               } else {
                  retval.append(ch);
               }
diff --git a/lucene/queryparser/src/java/org/apache/lucene/queryparser/classic/TokenMgrError.java b/lucene/queryparser/src/java/org/apache/lucene/queryparser/classic/TokenMgrError.java
index ad111d0cd26..17abedfefb5 100644
--- a/lucene/queryparser/src/java/org/apache/lucene/queryparser/classic/TokenMgrError.java
+++ b/lucene/queryparser/src/java/org/apache/lucene/queryparser/classic/TokenMgrError.java
@@ -82,7 +82,7 @@ public class TokenMgrError extends Error
         default:
           if ((ch = str.charAt(i)) < 0x20 || ch > 0x7e) {
             String s = "0000" + Integer.toString(ch, 16);
-            retval.append("\\u" + s.substring(s.length() - 4, s.length()));
+            retval.append("\\u").append(s.substring(s.length() - 4, s.length()));
           } else {
             retval.append(ch);
           }
diff --git a/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/AnyQueryNode.java b/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/AnyQueryNode.java
index a6874eee448..1e1592eee45 100644
--- a/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/AnyQueryNode.java
+++ b/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/AnyQueryNode.java
@@ -109,8 +109,7 @@ public class AnyQueryNode extends AndQueryNode {
       return "<any field='" + this.field + "'  matchelements="
           + this.minimumMatchingmElements + "/>";
     StringBuilder sb = new StringBuilder();
-    sb.append("<any field='" + this.field + "'  matchelements="
-        + this.minimumMatchingmElements + ">");
+    sb.append("<any field='").append(this.field).append("'  matchelements=").append(this.minimumMatchingmElements).append('>');
     for (QueryNode clause : getChildren()) {
       sb.append("\n");
       sb.append(clause.toString());
diff --git a/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/ProximityQueryNode.java b/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/ProximityQueryNode.java
index 4237e73eb59..9dfd65b4daf 100644
--- a/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/ProximityQueryNode.java
+++ b/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/nodes/ProximityQueryNode.java
@@ -150,8 +150,7 @@ public class ProximityQueryNode extends BooleanQueryNode {
           + "' type='" + this.proximityType.toString() + "'" + distanceSTR
           + "/>";
     StringBuilder sb = new StringBuilder();
-    sb.append("<proximity field='" + this.field + "' inorder='" + this.inorder
-        + "' type='" + this.proximityType.toString() + "'" + distanceSTR + ">");
+    sb.append("<proximity field='").append(this.field).append("' inorder='").append(this.inorder).append("' type='").append(this.proximityType.toString()).append("'").append(distanceSTR).append(">");
     for (QueryNode child : getChildren()) {
       sb.append("\n");
       sb.append(child.toString());
diff --git a/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/standard/parser/ParseException.java b/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/standard/parser/ParseException.java
index c3511a178a4..dadcb99c6c2 100644
--- a/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/standard/parser/ParseException.java
+++ b/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/standard/parser/ParseException.java
@@ -176,7 +176,7 @@ public class ParseException extends QueryNodeParseException {
            default:
               if ((ch = str.charAt(i)) < 0x20 || ch > 0x7e) {
                  String s = "0000" + Integer.toString(ch, 16);
-                 retval.append("\\u" + s.substring(s.length() - 4, s.length()));
+                 retval.append("\\u").append(s.substring(s.length() - 4, s.length()));
               } else {
                  retval.append(ch);
               }
diff --git a/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/standard/parser/TokenMgrError.java b/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/standard/parser/TokenMgrError.java
index f2ef4a57eb3..2cab350fcb5 100644
--- a/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/standard/parser/TokenMgrError.java
+++ b/lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/standard/parser/TokenMgrError.java
@@ -82,7 +82,7 @@ public class TokenMgrError extends Error
         default:
           if ((ch = str.charAt(i)) < 0x20 || ch > 0x7e) {
             String s = "0000" + Integer.toString(ch, 16);
-            retval.append("\\u" + s.substring(s.length() - 4, s.length()));
+            retval.append("\\u").append(s.substring(s.length() - 4, s.length()));
           } else {
             retval.append(ch);
           }
diff --git a/lucene/queryparser/src/java/org/apache/lucene/queryparser/surround/parser/ParseException.java b/lucene/queryparser/src/java/org/apache/lucene/queryparser/surround/parser/ParseException.java
index 4059bda68cc..6924da1b388 100644
--- a/lucene/queryparser/src/java/org/apache/lucene/queryparser/surround/parser/ParseException.java
+++ b/lucene/queryparser/src/java/org/apache/lucene/queryparser/surround/parser/ParseException.java
@@ -173,7 +173,7 @@ public class ParseException extends Exception {
            default:
               if ((ch = str.charAt(i)) < 0x20 || ch > 0x7e) {
                  String s = "0000" + Integer.toString(ch, 16);
-                 retval.append("\\u" + s.substring(s.length() - 4, s.length()));
+                 retval.append("\\u").append(s.substring(s.length() - 4, s.length()));
               } else {
                  retval.append(ch);
               }
diff --git a/lucene/queryparser/src/java/org/apache/lucene/queryparser/surround/parser/TokenMgrError.java b/lucene/queryparser/src/java/org/apache/lucene/queryparser/surround/parser/TokenMgrError.java
index 77e740f34ba..ba3297e855c 100644
--- a/lucene/queryparser/src/java/org/apache/lucene/queryparser/surround/parser/TokenMgrError.java
+++ b/lucene/queryparser/src/java/org/apache/lucene/queryparser/surround/parser/TokenMgrError.java
@@ -82,7 +82,7 @@ public class TokenMgrError extends Error
         default:
           if ((ch = str.charAt(i)) < 0x20 || ch > 0x7e) {
             String s = "0000" + Integer.toString(ch, 16);
-            retval.append("\\u" + s.substring(s.length() - 4, s.length()));
+            retval.append("\\u").append(s.substring(s.length() - 4, s.length()));
           } else {
             retval.append(ch);
           }
diff --git a/lucene/sandbox/src/java/org/apache/lucene/document/LatLonShapeLineQuery.java b/lucene/sandbox/src/java/org/apache/lucene/document/LatLonShapeLineQuery.java
index e7933457c3c..fcc2590dfdf 100644
--- a/lucene/sandbox/src/java/org/apache/lucene/document/LatLonShapeLineQuery.java
+++ b/lucene/sandbox/src/java/org/apache/lucene/document/LatLonShapeLineQuery.java
@@ -111,7 +111,7 @@ final class LatLonShapeLineQuery extends LatLonShapeQuery {
       sb.append(this.field);
       sb.append(':');
     }
-    sb.append("Line(" + lines[0].toGeoJSON() + ")");
+    sb.append("Line(").append(lines[0].toGeoJSON()).append(')');
     return sb.toString();
   }
 
diff --git a/lucene/sandbox/src/java/org/apache/lucene/document/LatLonShapePolygonQuery.java b/lucene/sandbox/src/java/org/apache/lucene/document/LatLonShapePolygonQuery.java
index 94dde0d4948..97e739ea5b7 100644
--- a/lucene/sandbox/src/java/org/apache/lucene/document/LatLonShapePolygonQuery.java
+++ b/lucene/sandbox/src/java/org/apache/lucene/document/LatLonShapePolygonQuery.java
@@ -100,7 +100,7 @@ final class LatLonShapePolygonQuery extends LatLonShapeQuery {
       sb.append(this.field);
       sb.append(':');
     }
-    sb.append("Polygon(" + polygons[0].toGeoJSON() + ")");
+    sb.append("Polygon(").append(polygons[0].toGeoJSON()).append(')');
     return sb.toString();
   }
 
diff --git a/lucene/sandbox/src/java/org/apache/lucene/geo/Tessellator.java b/lucene/sandbox/src/java/org/apache/lucene/geo/Tessellator.java
index 195e4a6c4d3..950ebd8e987 100644
--- a/lucene/sandbox/src/java/org/apache/lucene/geo/Tessellator.java
+++ b/lucene/sandbox/src/java/org/apache/lucene/geo/Tessellator.java
@@ -873,12 +873,12 @@ final public class Tessellator {
       if (this.previous == null)
         builder.append("||-");
       else
-        builder.append(this.previous.idx + " <- ");
+        builder.append(this.previous.idx).append(" <- ");
       builder.append(this.idx);
       if (this.next == null)
         builder.append(" -||");
       else
-        builder.append(" -> " + this.next.idx);
+        builder.append(" -> ").append(this.next.idx);
       return builder.toString();
     }
   }
diff --git a/lucene/sandbox/src/java/org/apache/lucene/search/TermAutomatonQuery.java b/lucene/sandbox/src/java/org/apache/lucene/search/TermAutomatonQuery.java
index cd123af3693..ff2147e50bf 100644
--- a/lucene/sandbox/src/java/org/apache/lucene/search/TermAutomatonQuery.java
+++ b/lucene/sandbox/src/java/org/apache/lucene/search/TermAutomatonQuery.java
@@ -284,9 +284,9 @@ public class TermAutomatonQuery extends Query {
       b.append("  ");
       b.append(state);
       if (det.isAccept(state)) {
-        b.append(" [shape=doublecircle,label=\"" + state + "\"]\n");
+        b.append(" [shape=doublecircle,label=\"").append(state).append("\"]\n");
       } else {
-        b.append(" [shape=circle,label=\"" + state + "\"]\n");
+        b.append(" [shape=circle,label=\"").append(state).append("\"]\n");
       }
       int numTransitions = det.initTransition(state, t);
       for(int i=0;i<numTransitions;i++) {
diff --git a/lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/NumberRangePrefixTreeStrategy.java b/lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/NumberRangePrefixTreeStrategy.java
index d720215ad9d..3d4c7a9b1f4 100644
--- a/lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/NumberRangePrefixTreeStrategy.java
+++ b/lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/NumberRangePrefixTreeStrategy.java
@@ -191,7 +191,7 @@ public class NumberRangePrefixTreeStrategy extends RecursivePrefixTreeStrategy {
     @Override
     public String toString() {
       StringBuilder buf = new StringBuilder(2048);
-      buf.append("Facets: level=" + detailLevel + " topLeaves=" + topLeaves + " parentCount=" + parents.size());
+      buf.append("Facets: level=").append(detailLevel).append(" topLeaves=").append(topLeaves).append(" parentCount=").append(parents.size());
       for (Map.Entry<UnitNRShape, FacetParentVal> entry : parents.entrySet()) {
         buf.append('\n');
         if (buf.length() > 1000) {
@@ -199,7 +199,7 @@ public class NumberRangePrefixTreeStrategy extends RecursivePrefixTreeStrategy {
           break;
         }
         final FacetParentVal pVal = entry.getValue();
-        buf.append(' ').append(entry.getKey()+" leafCount=" + pVal.parentLeaves);
+        buf.append(' ').append(entry.getKey()).append(" leafCount=").append(pVal.parentLeaves);
         if (pVal.childCounts != null) {
           buf.append(' ').append(Arrays.toString(pVal.childCounts));
         }
diff --git a/lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/RecursivePrefixTreeStrategy.java b/lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/RecursivePrefixTreeStrategy.java
index 59b636ccaa8..6591de96c1a 100644
--- a/lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/RecursivePrefixTreeStrategy.java
+++ b/lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/RecursivePrefixTreeStrategy.java
@@ -116,7 +116,7 @@ public class RecursivePrefixTreeStrategy extends PrefixTreeStrategy {
     if (pruneLeafyBranches)
       str.append(",pruneLeafyBranches");
     if (prefixGridScanLevel != grid.getMaxLevels() - 4)
-      str.append(",prefixGridScanLevel:").append(""+prefixGridScanLevel);
+      str.append(",prefixGridScanLevel:").append("").append(prefixGridScanLevel);
     if (!multiOverlappingIndexedShapes)
       str.append(",!multiOverlappingIndexedShapes");
     return str.append(')').toString();
diff --git a/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPoint.java b/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPoint.java
index fd4847621bd..748d11c2e31 100644
--- a/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPoint.java
+++ b/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPoint.java
@@ -186,9 +186,9 @@ public final class Geo3DPoint extends Field {
     result.append(':');
 
     BytesRef bytes = (BytesRef) fieldsData;
-    result.append(" x=" + decodeDimension(bytes.bytes, bytes.offset));
-    result.append(" y=" + decodeDimension(bytes.bytes, bytes.offset + Integer.BYTES));
-    result.append(" z=" + decodeDimension(bytes.bytes, bytes.offset + 2*Integer.BYTES));
+    result.append(" x=").append(decodeDimension(bytes.bytes, bytes.offset));
+    result.append(" y=").append(decodeDimension(bytes.bytes, bytes.offset + Integer.BYTES));
+    result.append(" z=").append(decodeDimension(bytes.bytes, bytes.offset + 2 * Integer.BYTES));
     result.append('>');
     return result.toString();
   }
diff --git a/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPointOutsideSortField.java b/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPointOutsideSortField.java
index 3f37b22f1fc..55cd985784e 100644
--- a/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPointOutsideSortField.java
+++ b/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPointOutsideSortField.java
@@ -85,7 +85,7 @@ final class Geo3DPointOutsideSortField extends SortField {
     builder.append(" shape=");
     builder.append(distanceShape);
     if (Double.POSITIVE_INFINITY != getMissingValue()) {
-      builder.append(" missingValue=" + getMissingValue());
+      builder.append(" missingValue=").append(getMissingValue());
     }
     builder.append('>');
     return builder.toString();
diff --git a/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPointSortField.java b/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPointSortField.java
index bf1de774658..476ef943642 100644
--- a/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPointSortField.java
+++ b/lucene/spatial3d/src/java/org/apache/lucene/spatial3d/Geo3DPointSortField.java
@@ -85,7 +85,7 @@ final class Geo3DPointSortField extends SortField {
     builder.append(" shape=");
     builder.append(distanceShape);
     if (Double.POSITIVE_INFINITY != getMissingValue()) {
-      builder.append(" missingValue=" + getMissingValue());
+      builder.append(" missingValue=").append(getMissingValue());
     }
     builder.append('>');
     return builder.toString();
diff --git a/lucene/suggest/src/java/org/apache/lucene/search/suggest/jaspell/JaspellTernarySearchTrie.java b/lucene/suggest/src/java/org/apache/lucene/search/suggest/jaspell/JaspellTernarySearchTrie.java
index 3900a626e8d..d60c6043ac1 100644
--- a/lucene/suggest/src/java/org/apache/lucene/search/suggest/jaspell/JaspellTernarySearchTrie.java
+++ b/lucene/suggest/src/java/org/apache/lucene/search/suggest/jaspell/JaspellTernarySearchTrie.java
@@ -439,14 +439,14 @@ public class JaspellTernarySearchTrie implements Accountable {
   protected String getKey(TSTNode node) {
     StringBuilder getKeyBuffer = new StringBuilder();
     getKeyBuffer.setLength(0);
-    getKeyBuffer.append("" + node.splitchar);
+    getKeyBuffer.append("").append(node.splitchar);
     TSTNode currentNode;
     TSTNode lastNode;
     currentNode = node.relatives[TSTNode.PARENT];
     lastNode = node;
     while (currentNode != null) {
       if (currentNode.relatives[TSTNode.EQKID] == lastNode) {
-        getKeyBuffer.append("" + currentNode.splitchar);
+        getKeyBuffer.append("").append(currentNode.splitchar);
       }
       lastNode = currentNode;
       currentNode = currentNode.relatives[TSTNode.PARENT];
diff --git a/lucene/test-framework/src/java/org/apache/lucene/geo/BaseGeoPointTestCase.java b/lucene/test-framework/src/java/org/apache/lucene/geo/BaseGeoPointTestCase.java
index 741e79423a9..066716aaacf 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/geo/BaseGeoPointTestCase.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/geo/BaseGeoPointTestCase.java
@@ -856,17 +856,17 @@ public abstract class BaseGeoPointTestCase extends LuceneTestCase {
 
         if (hits.get(docID) != expected) {
           StringBuilder b = new StringBuilder();
-          b.append("docID=(" + docID + ")\n");
+          b.append("docID=(").append(docID).append(")\n");
 
           if (expected) {
-            b.append("FAIL: id=" + id + " should match but did not\n");
+            b.append("FAIL: id=").append(id).append(" should match but did not\n");
           } else {
-            b.append("FAIL: id=" + id + " should not match but did\n");
+            b.append("FAIL: id=").append(id).append(" should not match but did\n");
           }
-          b.append("  box=" + rect + "\n");
-          b.append("  query=" + query + " docID=" + docID + "\n");
-          b.append("  lat=" + lats[id] + " lon=" + lons[id] + "\n");
-          b.append("  deleted?=" + (liveDocs != null && liveDocs.get(docID) == false));
+          b.append("  box=").append(rect).append("\n");
+          b.append("  query=").append(query).append(" docID=").append(docID).append("\n");
+          b.append("  lat=").append(lats[id]).append(" lon=").append(lons[id]).append("\n");
+          b.append("  deleted?=").append(liveDocs != null && liveDocs.get(docID) == false);
           if (true) {
             fail("wrong hit (first of possibly more):\n\n" + b);
           } else {
@@ -997,16 +997,16 @@ public abstract class BaseGeoPointTestCase extends LuceneTestCase {
           StringBuilder b = new StringBuilder();
 
           if (expected) {
-            b.append("FAIL: id=" + id + " should match but did not\n");
+            b.append("FAIL: id=").append(id).append(" should match but did not\n");
           } else {
-            b.append("FAIL: id=" + id + " should not match but did\n");
+            b.append("FAIL: id=").append(id).append(" should not match but did\n");
           }
-          b.append("  query=" + query + " docID=" + docID + "\n");
-          b.append("  lat=" + lats[id] + " lon=" + lons[id] + "\n");
-          b.append("  deleted?=" + (liveDocs != null && liveDocs.get(docID) == false));
+          b.append("  query=").append(query).append(" docID=").append(docID).append("\n");
+          b.append("  lat=").append(lats[id]).append(" lon=").append(lons[id]).append("\n");
+          b.append("  deleted?=").append(liveDocs != null && liveDocs.get(docID) == false);
           if (Double.isNaN(lats[id]) == false) {
             double distanceMeters = SloppyMath.haversinMeters(centerLat, centerLon, lats[id], lons[id]);
-            b.append("  centerLat=" + centerLat + " centerLon=" + centerLon + " distanceMeters=" + distanceMeters + " vs radiusMeters=" + radiusMeters);
+            b.append("  centerLat=").append(centerLat).append(" centerLon=").append(centerLon).append(" distanceMeters=").append(distanceMeters).append(" vs radiusMeters=").append(radiusMeters);
           }
           if (true) {
             fail("wrong hit (first of possibly more):\n\n" + b);
@@ -1129,14 +1129,14 @@ public abstract class BaseGeoPointTestCase extends LuceneTestCase {
           StringBuilder b = new StringBuilder();
 
           if (expected) {
-            b.append("FAIL: id=" + id + " should match but did not\n");
+            b.append("FAIL: id=").append(id).append(" should match but did not\n");
           } else {
-            b.append("FAIL: id=" + id + " should not match but did\n");
+            b.append("FAIL: id=").append(id).append(" should not match but did\n");
           }
-          b.append("  query=" + query + " docID=" + docID + "\n");
-          b.append("  lat=" + lats[id] + " lon=" + lons[id] + "\n");
-          b.append("  deleted?=" + (liveDocs != null && liveDocs.get(docID) == false));
-          b.append("  polygon=" + polygon);
+          b.append("  query=").append(query).append(" docID=").append(docID).append("\n");
+          b.append("  lat=").append(lats[id]).append(" lon=").append(lons[id]).append("\n");
+          b.append("  deleted?=").append(liveDocs != null && liveDocs.get(docID) == false);
+          b.append("  polygon=").append(polygon);
           if (true) {
             fail("wrong hit (first of possibly more):\n\n" + b);
           } else {
diff --git a/lucene/test-framework/src/java/org/apache/lucene/geo/EarthDebugger.java b/lucene/test-framework/src/java/org/apache/lucene/geo/EarthDebugger.java
index 3553b1576a8..59beb398b3e 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/geo/EarthDebugger.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/geo/EarthDebugger.java
@@ -46,7 +46,7 @@ public class EarthDebugger {
     b.append("    <script src=\"http://www.webglearth.com/v2/api.js\"></script>\n");
     b.append("    <script>\n");
     b.append("      function initialize() {\n");
-    b.append("        var earth = new WE.map('earth_div', {center: [" + centerLat + ", " + centerLon + "], altitude: " + altitudeMeters + "});\n");
+    b.append("        var earth = new WE.map('earth_div', {center: [").append(centerLat).append(", ").append(centerLon).append("], altitude: ").append(altitudeMeters).append("});\n");
   }
 
   public void addPolygon(Polygon poly) {
@@ -57,14 +57,14 @@ public class EarthDebugger {
     String name = "poly" + nextShape;
     nextShape++;
 
-    b.append("        var " + name + " = WE.polygon([\n");
+    b.append("        var ").append(name).append(" = WE.polygon([\n");
     double[] polyLats = poly.getPolyLats();
     double[] polyLons = poly.getPolyLons();
     for(int i=0;i<polyLats.length;i++) {
-      b.append("          [" + polyLats[i] + ", " + polyLons[i] + "],\n");
+      b.append("          [").append(polyLats[i]).append(", ").append(polyLons[i]).append("],\n");
     }
-    b.append("        ], {color: '" + color + "', fillColor: \"#000000\", fillOpacity: 0.0001});\n");
-    b.append("        " + name + ".addTo(earth);\n");
+    b.append("        ], {color: '").append(color).append("', fillColor: \"#000000\", fillOpacity: 0.0001});\n");
+    b.append("        ").append(name).append(".addTo(earth);\n");
 
     for (Polygon hole : poly.getHoles()) {
       addPolygon(hole, "#ffffff");
@@ -84,7 +84,7 @@ public class EarthDebugger {
   private void drawSegment(double minLat, double maxLat, double minLon, double maxLon) {
     int steps = getStepCount(minLat, maxLat, minLon, maxLon);
     for(int i=0;i<steps;i++) {
-      b.append("          [" + (minLat + (maxLat - minLat) * i / steps) + ", " + (minLon + (maxLon - minLon) * i / steps) + "],\n");
+      b.append("          [").append(minLat + (maxLat - minLat) * i / steps).append(", ").append(minLon + (maxLon - minLon) * i / steps).append("],\n");
     }
   }
 
@@ -96,8 +96,8 @@ public class EarthDebugger {
     String name = "rect" + nextShape;
     nextShape++;
 
-    b.append("        // lat: " + minLat + " TO " + maxLat + "; lon: " + minLon + " TO " + maxLon + "\n");
-    b.append("        var " + name + " = WE.polygon([\n");
+    b.append("        // lat: ").append(minLat).append(" TO ").append(maxLat).append("; lon: ").append(minLon).append(" TO ").append(maxLon).append("\n");
+    b.append("        var ").append(name).append(" = WE.polygon([\n");
 
     b.append("          // min -> max lat, min lon\n");
     drawSegment(minLat, maxLat, minLon, minLon);
@@ -112,9 +112,9 @@ public class EarthDebugger {
     drawSegment(minLat, minLat, maxLon, minLon);
 
     b.append("          // min lat, min lon\n");
-    b.append("          [" + minLat + ", " + minLon + "]\n");
-    b.append("        ], {color: \"" + color + "\", fillColor: \"" + color + "\"});\n");
-    b.append("        " + name + ".addTo(earth);\n");
+    b.append("          [").append(minLat).append(", ").append(minLon).append("]\n");
+    b.append("        ], {color: \"").append(color).append("\", fillColor: \"").append(color).append("\"});\n");
+    b.append("        ").append(name).append(".addTo(earth);\n");
   }
 
   /** Draws a line a fixed latitude, spanning the min/max longitude */
@@ -122,19 +122,19 @@ public class EarthDebugger {
     String name = "latline" + nextShape;
     nextShape++;
 
-    b.append("        var " + name + " = WE.polygon([\n");
+    b.append("        var ").append(name).append(" = WE.polygon([\n");
     double lon;
     int steps = getStepCount(lat, minLon, lat, maxLon);
     for(lon = minLon;lon<=maxLon;lon += (maxLon-minLon)/steps) {
-      b.append("          [" + lat + ", " + lon + "],\n");
+      b.append("          [").append(lat).append(", ").append(lon).append("],\n");
     }
-    b.append("          [" + lat + ", " + maxLon + "],\n");
+    b.append("          [").append(lat).append(", ").append(maxLon).append("],\n");
     lon -= (maxLon-minLon)/steps;
     for(;lon>=minLon;lon -= (maxLon-minLon)/steps) {
-      b.append("          [" + lat + ", " + lon + "],\n");
+      b.append("          [").append(lat).append(", ").append(lon).append("],\n");
     }
     b.append("        ], {color: \"#ff0000\", fillColor: \"#ffffff\", opacity: 1, fillOpacity: 0.0001});\n");
-    b.append("        " + name + ".addTo(earth);\n");
+    b.append("        ").append(name).append(".addTo(earth);\n");
   }
 
   /** Draws a line a fixed longitude, spanning the min/max latitude */
@@ -142,33 +142,33 @@ public class EarthDebugger {
     String name = "lonline" + nextShape;
     nextShape++;
 
-    b.append("        var " + name + " = WE.polygon([\n");
+    b.append("        var ").append(name).append(" = WE.polygon([\n");
     double lat;
     int steps = getStepCount(minLat, lon, maxLat, lon);
     for(lat = minLat;lat<=maxLat;lat += (maxLat-minLat)/steps) {
-      b.append("          [" + lat + ", " + lon + "],\n");
+      b.append("          [").append(lat).append(", ").append(lon).append("],\n");
     }
-    b.append("          [" + maxLat + ", " + lon + "],\n");
+    b.append("          [").append(maxLat).append(", ").append(lon).append("],\n");
     lat -= (maxLat-minLat)/36;
     for(;lat>=minLat;lat -= (maxLat-minLat)/steps) {
-      b.append("          [" + lat + ", " + lon + "],\n");
+      b.append("          [").append(lat).append(", ").append(lon).append("],\n");
     }
     b.append("        ], {color: \"#ff0000\", fillColor: \"#ffffff\", opacity: 1, fillOpacity: 0.0001});\n");
-    b.append("        " + name + ".addTo(earth);\n");
+    b.append("        ").append(name).append(".addTo(earth);\n");
   }
 
   public void addPoint(double lat, double lon) {
-    b.append("        WE.marker([" + lat + ", " + lon + "]).addTo(earth);\n");    
+    b.append("        WE.marker([").append(lat).append(", ").append(lon).append("]).addTo(earth);\n");
   }
 
   public void addCircle(double centerLat, double centerLon, double radiusMeters, boolean alsoAddBBox) {
     addPoint(centerLat, centerLon);
     String name = "circle" + nextShape;
     nextShape++;
-    b.append("        var " + name + " = WE.polygon([\n");
+    b.append("        var ").append(name).append(" = WE.polygon([\n");
     inverseHaversin(b, centerLat, centerLon, radiusMeters);
     b.append("        ], {color: '#00ff00', fillColor: \"#000000\", fillOpacity: 0.0001 });\n");
-    b.append("        " + name + ".addTo(earth);\n");
+    b.append("        ").append(name).append(".addTo(earth);\n");
 
     if (alsoAddBBox) {
       Rectangle box = Rectangle.fromPointDistance(centerLat, centerLon, radiusMeters);
@@ -235,7 +235,7 @@ public class EarthDebugger {
 
         //System.out.println("  iter lat=" + lat + " lon=" + lon + " distance=" + distanceMeters + " vs " + radiusMeters);
         if (Math.abs(distanceMeters - radiusMeters) < 0.1) {
-          b.append("          [" + lat + ", " + lon + "],\n");
+          b.append("          [").append(lat).append(", ").append(lon).append("],\n");
           break;
         }
         if (distanceMeters > radiusMeters) {
diff --git a/lucene/test-framework/src/java/org/apache/lucene/geo/GeoTestUtil.java b/lucene/test-framework/src/java/org/apache/lucene/geo/GeoTestUtil.java
index c5a4afe56b4..aec09789190 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/geo/GeoTestUtil.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/geo/GeoTestUtil.java
@@ -590,10 +590,10 @@ public class GeoTestUtil {
       if (o instanceof double[]) {
         double point[] = (double[]) o;
         sb.append("<!-- point: ");
-        sb.append(point[0] + "," + point[1]);
+        sb.append(point[0]).append(',').append(point[1]);
         sb.append(" -->\n");
       } else {
-        sb.append("<!-- " + o.getClass().getSimpleName() + ": \n");
+        sb.append("<!-- ").append(o.getClass().getSimpleName()).append(": \n");
         sb.append(o.toString());
         sb.append("\n-->\n");
       }
@@ -620,7 +620,7 @@ public class GeoTestUtil {
       // polygon
       double polyLats[] = gon.getPolyLats();
       double polyLons[] = gon.getPolyLons();
-      sb.append("<polygon fill-opacity=\"" + opacity + "\" points=\"");
+      sb.append("<polygon fill-opacity=\"").append(opacity).append("\" points=\"");
       for (int i = 0; i < polyLats.length; i++) {
         if (i > 0) {
           sb.append(" ");
@@ -629,7 +629,7 @@ public class GeoTestUtil {
         .append(",")
         .append(90 - polyLats[i]);
       }
-      sb.append("\" style=\"" + style + "\"/>\n");
+      sb.append("\" style=\"").append(style).append("\"/>\n");
       for (Polygon hole : gon.getHoles()) {
         double holeLats[] = hole.getPolyLats();
         double holeLons[] = hole.getPolyLons();
diff --git a/lucene/test-framework/src/java/org/apache/lucene/search/BaseRangeFieldQueryTestCase.java b/lucene/test-framework/src/java/org/apache/lucene/search/BaseRangeFieldQueryTestCase.java
index e4a97d00156..09a8e89220b 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/search/BaseRangeFieldQueryTestCase.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/search/BaseRangeFieldQueryTestCase.java
@@ -272,20 +272,20 @@ public abstract class BaseRangeFieldQueryTestCase extends LuceneTestCase {
 
         if (hits.get(docID) != expected) {
           StringBuilder b = new StringBuilder();
-          b.append("FAIL (iter " + iter + "): ");
+          b.append("FAIL (iter ").append(iter).append("): ");
           if (expected == true) {
-            b.append("id=" + id + (ranges[id].length > 1 ? " (MultiValue) " : " ") + "should match but did not\n");
+            b.append("id=").append(id).append(ranges[id].length > 1 ? " (MultiValue) " : " ").append("should match but did not\n");
           } else {
-            b.append("id=" + id + " should not match but did\n");
+            b.append("id=").append(id).append(" should not match but did\n");
           }
-          b.append(" queryRange=" + queryRange + "\n");
-          b.append(" box" + ((ranges[id].length > 1) ? "es=" : "=" ) + ranges[id][0]);
+          b.append(" queryRange=").append(queryRange).append("\n");
+          b.append(" box").append((ranges[id].length > 1) ? "es=" : "=").append(ranges[id][0]);
           for (int n=1; n<ranges[id].length; ++n) {
             b.append(", ");
             b.append(ranges[id][n]);
           }
-          b.append("\n queryType=" + queryType + "\n");
-          b.append(" deleted?=" + (liveDocs != null && liveDocs.get(docID) == false));
+          b.append("\n queryType=").append(queryType).append("\n");
+          b.append(" deleted?=").append(liveDocs != null && liveDocs.get(docID) == false);
           fail("wrong hit (first of possibly more):\n\n" + b);
         }
       }
diff --git a/lucene/test-framework/src/java/org/apache/lucene/util/LuceneTestCase.java b/lucene/test-framework/src/java/org/apache/lucene/util/LuceneTestCase.java
index 92d364d04bf..ae73b3ff032 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/util/LuceneTestCase.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/util/LuceneTestCase.java
@@ -1284,8 +1284,8 @@ public abstract class LuceneTestCase extends Assert {
       if (previousLines.length == currentLines.length) {
         for (int i = 0; i < previousLines.length; i++) {
           if (!previousLines[i].equals(currentLines[i])) {
-            diff.append("- " + previousLines[i] + "\n");
-            diff.append("+ " + currentLines[i] + "\n");
+            diff.append("- ").append(previousLines[i]).append("\n");
+            diff.append("+ ").append(currentLines[i]).append("\n");
           }
         }
       } else {
diff --git a/lucene/tools/src/java/org/apache/lucene/validation/LicenseCheckTask.java b/lucene/tools/src/java/org/apache/lucene/validation/LicenseCheckTask.java
index e26df804320..c835b666e8d 100644
--- a/lucene/tools/src/java/org/apache/lucene/validation/LicenseCheckTask.java
+++ b/lucene/tools/src/java/org/apache/lucene/validation/LicenseCheckTask.java
@@ -304,9 +304,7 @@ outer:
     if (foundLicenses.isEmpty()) {
       this.failures = true;
       StringBuilder message = new StringBuilder();
-      message.append(
-          "MISSING LICENSE for the following file:\n  " + jarFile.getAbsolutePath()
-          + "\n  Expected locations below:\n");
+      message.append("MISSING LICENSE for the following file:\n  ").append(jarFile.getAbsolutePath()).append("\n  Expected locations below:\n");
       for (File location : expectedLocations) {
         message.append("  => ").append(location.getAbsolutePath()).append("\n");
       }
diff --git a/solr/contrib/extraction/src/java/org/apache/solr/handler/extraction/XLSXResponseWriter.java b/solr/contrib/extraction/src/java/org/apache/solr/handler/extraction/XLSXResponseWriter.java
index a673d30604d..9264a1d97e5 100644
--- a/solr/contrib/extraction/src/java/org/apache/solr/handler/extraction/XLSXResponseWriter.java
+++ b/solr/contrib/extraction/src/java/org/apache/solr/handler/extraction/XLSXResponseWriter.java
@@ -284,12 +284,12 @@ class XLSXWriter extends TabularResponseWriter {
       if (v instanceof IndexableField) {
         IndexableField f = (IndexableField)v;
         if (v instanceof Date) {
-          output.append(((Date) val).toInstant().toString() + "; ");
+          output.append(((Date) val).toInstant().toString()).append("; ");
         } else {
-          output.append(f.stringValue() + "; ");
+          output.append(f.stringValue()).append("; ");
         }
       } else {
-        output.append(v.toString() + "; ");
+        output.append(v.toString()).append("; ");
       }
     }
     if (output.length() > 0) {
diff --git a/solr/core/src/java/org/apache/solr/cloud/autoscaling/sim/SimCloudManager.java b/solr/core/src/java/org/apache/solr/cloud/autoscaling/sim/SimCloudManager.java
index 01ab2270772..6e27599b4d6 100644
--- a/solr/core/src/java/org/apache/solr/cloud/autoscaling/sim/SimCloudManager.java
+++ b/solr/core/src/java/org/apache/solr/cloud/autoscaling/sim/SimCloudManager.java
@@ -387,7 +387,7 @@ public class SimCloudManager implements SolrCloudManager {
     sb.append("#######################################\n");
     sb.append("############ CLUSTER STATE ############\n");
     sb.append("#######################################\n");
-    sb.append("## Live nodes:\t\t" + getLiveNodesSet().size() + "\n");
+    sb.append("## Live nodes:\t\t").append(getLiveNodesSet().size()).append("\n");
     int emptyNodes = 0;
     int maxReplicas = 0;
     int minReplicas = Integer.MAX_VALUE;
@@ -414,37 +414,37 @@ public class SimCloudManager implements SolrCloudManager {
     if (minReplicas == Integer.MAX_VALUE) {
       minReplicas = 0;
     }
-    sb.append("## Empty nodes:\t" + emptyNodes + "\n");
+    sb.append("## Empty nodes:\t").append(emptyNodes).append("\n");
     Set<String> deadNodes = getSimNodeStateProvider().simGetDeadNodes();
-    sb.append("## Dead nodes:\t\t" + deadNodes.size() + "\n");
-    deadNodes.forEach(n -> sb.append("##\t\t" + n + "\n"));
+    sb.append("## Dead nodes:\t\t").append(deadNodes.size()).append("\n");
+    deadNodes.forEach(n -> sb.append("##\t\t").append(n).append("\n"));
     sb.append("## Collections:\n");
       clusterStateProvider.simGetCollectionStats().forEach((coll, stats) -> {
         sb.append("##  * ").append(coll).append('\n');
         stats.forEach((k, v) -> {
-          sb.append("##    " + k + "\t" + v + "\n");
+          sb.append("##    ").append(k).append("\t").append(v).append("\n");
         });
       });
     if (withCollections) {
       ClusterState state = clusterStateProvider.getClusterState();
-      state.forEachCollection(coll -> sb.append(coll.toString() + "\n"));
+      state.forEachCollection(coll -> sb.append(coll.toString()).append("\n"));
     }
-    sb.append("## Max replicas per node:\t" + maxReplicas + "\n");
-    sb.append("## Min replicas per node:\t" + minReplicas + "\n");
-    sb.append("## Total replicas:\t\t" + numReplicas + "\n");
+    sb.append("## Max replicas per node:\t").append(maxReplicas).append("\n");
+    sb.append("## Min replicas per node:\t").append(minReplicas).append("\n");
+    sb.append("## Total replicas:\t\t").append(numReplicas).append("\n");
     replicaStates.forEach((c, map) -> {
       AtomicInteger repCnt = new AtomicInteger();
       map.forEach((s, cnt) -> repCnt.addAndGet(cnt.get()));
-      sb.append("## * " + c + "\t\t" + repCnt.get() + "\n");
-      map.forEach((s, cnt) -> sb.append("##\t\t- " + String.format(Locale.ROOT, "%-12s  %4d", s, cnt.get()) + "\n"));
+      sb.append("## * ").append(c).append("\t\t").append(repCnt.get()).append("\n");
+      map.forEach((s, cnt) -> sb.append("##\t\t- ").append(String.format(Locale.ROOT, "%-12s  %4d", s, cnt.get())).append("\n"));
     });
     sb.append("######### Solr op counts ##########\n");
-    simGetOpCounts().forEach((k, cnt) -> sb.append("##\t\t- " + String.format(Locale.ROOT, "%-14s  %4d", k, cnt.get()) + "\n"));
+    simGetOpCounts().forEach((k, cnt) -> sb.append("##\t\t- ").append(String.format(Locale.ROOT, "%-14s  %4d", k, cnt.get())).append("\n"));
     sb.append("######### Autoscaling event counts ###########\n");
     Map<String, Map<String, AtomicInteger>> counts = simGetEventCounts();
     counts.forEach((trigger, map) -> {
-      sb.append("## * Trigger: " + trigger + "\n");
-      map.forEach((s, cnt) -> sb.append("##\t\t- " + String.format(Locale.ROOT, "%-11s  %4d", s, cnt.get()) + "\n"));
+      sb.append("## * Trigger: ").append(trigger).append("\n");
+      map.forEach((s, cnt) -> sb.append("##\t\t- ").append(String.format(Locale.ROOT, "%-11s  %4d", s, cnt.get())).append("\n"));
     });
     return sb.toString();
   }
diff --git a/solr/core/src/java/org/apache/solr/core/PluginInfo.java b/solr/core/src/java/org/apache/solr/core/PluginInfo.java
index 10f8b8d35d9..1bc85aeb0cd 100644
--- a/solr/core/src/java/org/apache/solr/core/PluginInfo.java
+++ b/solr/core/src/java/org/apache/solr/core/PluginInfo.java
@@ -108,11 +108,11 @@ public class PluginInfo implements MapSerializable {
   @Override
   public String toString() {
     StringBuilder sb = new StringBuilder("{");
-    if (type != null) sb.append("type = " + type + ",");
-    if (name != null) sb.append("name = " + name + ",");
-    if (className != null) sb.append("class = " + className + ",");
-    if (attributes != null && attributes.size() > 0) sb.append("attributes = " + attributes + ",");
-    if (initArgs != null && initArgs.size() > 0) sb.append("args = " + initArgs);
+    if (type != null) sb.append("type = ").append(type).append(',');
+    if (name != null) sb.append("name = ").append(name).append(',');
+    if (className != null) sb.append("class = ").append(className).append(',');
+    if (attributes != null && attributes.size() > 0) sb.append("attributes = ").append(attributes).append(',');
+    if (initArgs != null && initArgs.size() > 0) sb.append("args = ").append(initArgs);
     sb.append("}");
     return sb.toString();
   }
diff --git a/solr/core/src/java/org/apache/solr/handler/admin/SegmentsInfoRequestHandler.java b/solr/core/src/java/org/apache/solr/handler/admin/SegmentsInfoRequestHandler.java
index 3cc7a0926c9..2c0764eff35 100644
--- a/solr/core/src/java/org/apache/solr/handler/admin/SegmentsInfoRequestHandler.java
+++ b/solr/core/src/java/org/apache/solr/handler/admin/SegmentsInfoRequestHandler.java
@@ -350,8 +350,8 @@ public class SegmentsInfoRequestHandler extends RequestHandlerBase {
     flags.append( (fi.isSoftDeletesField() ? "s" : "-"));
     if (fi.getPointDataDimensionCount() > 0 || fi.getPointIndexDimensionCount() > 0) {
       flags.append(":");
-      flags.append(fi.getPointDataDimensionCount() + ":");
-      flags.append(fi.getPointIndexDimensionCount() + ":");
+      flags.append(fi.getPointDataDimensionCount()).append(':');
+      flags.append(fi.getPointIndexDimensionCount()).append(':');
       flags.append(fi.getPointNumBytes());
     }
 
diff --git a/solr/core/src/java/org/apache/solr/handler/export/SortDoc.java b/solr/core/src/java/org/apache/solr/handler/export/SortDoc.java
index d26746c6b75..5e2c75de0ea 100644
--- a/solr/core/src/java/org/apache/solr/handler/export/SortDoc.java
+++ b/solr/core/src/java/org/apache/solr/handler/export/SortDoc.java
@@ -118,9 +118,9 @@ class SortDoc {
 
   public String toString() {
     StringBuilder builder = new StringBuilder();
-    builder.append("docId: " + docId + "; ");
+    builder.append("docId: ").append(docId).append("; ");
     for (int i=0; i < sortValues.length; i++) {
-      builder.append("value" + i + ": " + sortValues[i] + ", ");
+      builder.append("value").append(i).append(": ").append(sortValues[i]).append(", ");
     }
     return builder.toString();
   }
diff --git a/solr/core/src/java/org/apache/solr/parser/ParseException.java b/solr/core/src/java/org/apache/solr/parser/ParseException.java
index 7732a7d5295..6806d6a0041 100644
--- a/solr/core/src/java/org/apache/solr/parser/ParseException.java
+++ b/solr/core/src/java/org/apache/solr/parser/ParseException.java
@@ -173,7 +173,7 @@ public class ParseException extends Exception {
            default:
               if ((ch = str.charAt(i)) < 0x20 || ch > 0x7e) {
                  String s = "0000" + Integer.toString(ch, 16);
-                 retval.append("\\u" + s.substring(s.length() - 4, s.length()));
+                 retval.append("\\u").append(s.substring(s.length() - 4, s.length()));
               } else {
                  retval.append(ch);
               }
diff --git a/solr/core/src/java/org/apache/solr/parser/TokenMgrError.java b/solr/core/src/java/org/apache/solr/parser/TokenMgrError.java
index ecdcc539d66..e50936f46ed 100644
--- a/solr/core/src/java/org/apache/solr/parser/TokenMgrError.java
+++ b/solr/core/src/java/org/apache/solr/parser/TokenMgrError.java
@@ -82,7 +82,7 @@ public class TokenMgrError extends Error
         default:
           if ((ch = str.charAt(i)) < 0x20 || ch > 0x7e) {
             String s = "0000" + Integer.toString(ch, 16);
-            retval.append("\\u" + s.substring(s.length() - 4, s.length()));
+            retval.append("\\u").append(s.substring(s.length() - 4, s.length()));
           } else {
             retval.append(ch);
           }
diff --git a/solr/core/src/java/org/apache/solr/schema/SimplePreAnalyzedParser.java b/solr/core/src/java/org/apache/solr/schema/SimplePreAnalyzedParser.java
index 0757d033fdc..3704b4e44e6 100644
--- a/solr/core/src/java/org/apache/solr/schema/SimplePreAnalyzedParser.java
+++ b/solr/core/src/java/org/apache/solr/schema/SimplePreAnalyzedParser.java
@@ -495,23 +495,23 @@ public final class SimplePreAnalyzedParser implements PreAnalyzedParser {
           } else {
             if (tok.length() > 0) tok.append(',');
             if (cl.isAssignableFrom(FlagsAttribute.class)) {
-              tok.append("f=" + Integer.toHexString(((FlagsAttribute)att).getFlags()));
+              tok.append("f=").append(Integer.toHexString(((FlagsAttribute) att).getFlags()));
             } else if (cl.isAssignableFrom(OffsetAttribute.class)) {
-              tok.append("s=" + ((OffsetAttribute)att).startOffset() + ",e=" + ((OffsetAttribute)att).endOffset());
+              tok.append("s=").append(((OffsetAttribute) att).startOffset()).append(",e=").append(((OffsetAttribute) att).endOffset());
             } else if (cl.isAssignableFrom(PayloadAttribute.class)) {
               BytesRef p = ((PayloadAttribute)att).getPayload();
               if (p != null && p.length > 0) {
-                tok.append("p=" + bytesToHex(p.bytes, p.offset, p.length));
+                tok.append("p=").append(bytesToHex(p.bytes, p.offset, p.length));
               } else if (tok.length() > 0) {
                 tok.setLength(tok.length() - 1); // remove the last comma
               }
             } else if (cl.isAssignableFrom(PositionIncrementAttribute.class)) {
-              tok.append("i=" + ((PositionIncrementAttribute)att).getPositionIncrement());
+              tok.append("i=").append(((PositionIncrementAttribute) att).getPositionIncrement());
             } else if (cl.isAssignableFrom(TypeAttribute.class)) {
-              tok.append("y=" + escape(((TypeAttribute)att).type()));
+              tok.append("y=").append(escape(((TypeAttribute) att).type()));
             } else {
               
-              tok.append(cl.getName() + "=" + escape(att.toString()));
+              tok.append(cl.getName()).append('=').append(escape(att.toString()));
             }
           }
         }
diff --git a/solr/core/src/java/org/apache/solr/search/QueryParsing.java b/solr/core/src/java/org/apache/solr/search/QueryParsing.java
index c7cd49cfab7..cc35c7811a0 100644
--- a/solr/core/src/java/org/apache/solr/search/QueryParsing.java
+++ b/solr/core/src/java/org/apache/solr/search/QueryParsing.java
@@ -178,7 +178,7 @@ public class QueryParsing {
     ft = schema.getFieldTypeNoEx(name);
     out.append(name);
     if (ft == null) {
-      out.append("(UNKNOWN FIELD " + name + ')');
+      out.append("(UNKNOWN FIELD ").append(name).append(String.valueOf(')'));
     }
     out.append(':');
     return ft;
@@ -328,12 +328,11 @@ public class QueryParsing {
     } else if (query instanceof BoostQuery) {
       BoostQuery q = (BoostQuery)query;
       toString(q.getQuery(), schema, out, subflag | FLAG_BOOSTED);
-      out.append("^");
+      out.append('^');
       out.append(Float.toString(q.getBoost()));
     }
     else {
-      out.append(query.getClass().getSimpleName()
-              + '(' + query.toString() + ')');
+      out.append(query.getClass().getSimpleName()).append('(').append(query.toString()).append(')');
     }
   }
 
diff --git a/solr/core/src/java/org/apache/solr/search/join/GraphQuery.java b/solr/core/src/java/org/apache/solr/search/join/GraphQuery.java
index accb1dc9298..5bec5997dc0 100644
--- a/solr/core/src/java/org/apache/solr/search/join/GraphQuery.java
+++ b/solr/core/src/java/org/apache/solr/search/join/GraphQuery.java
@@ -118,14 +118,14 @@ public class GraphQuery extends Query {
   @Override
   public String toString(String field) {
     StringBuilder sb = new StringBuilder();
-    sb.append("[[" + q.toString() + "]," + fromField + "=" + toField + "]");
+    sb.append("[[").append(q.toString()).append("],").append(fromField).append('=').append(toField).append(']');
     if (traversalFilter != null) {
-      sb.append(" [TraversalFilter: " + traversalFilter.toString() + "]");
+      sb.append(" [TraversalFilter: ").append(traversalFilter.toString()).append(']');
     }
-    sb.append("[maxDepth=" + maxDepth + "]");
-    sb.append("[returnRoot=" + returnRoot + "]");
-    sb.append("[onlyLeafNodes=" + onlyLeafNodes + "]");
-    sb.append("[useAutn=" + useAutn + "]");
+    sb.append("[maxDepth=").append(maxDepth).append(']');
+    sb.append("[returnRoot=").append(returnRoot).append(']');
+    sb.append("[onlyLeafNodes=").append(onlyLeafNodes).append(']');
+    sb.append("[useAutn=").append(useAutn).append(']');
     return sb.toString();
   }
   
diff --git a/solr/core/src/java/org/apache/solr/update/SolrCmdDistributor.java b/solr/core/src/java/org/apache/solr/update/SolrCmdDistributor.java
index cfdfb5117ad..59106849b10 100644
--- a/solr/core/src/java/org/apache/solr/update/SolrCmdDistributor.java
+++ b/solr/core/src/java/org/apache/solr/update/SolrCmdDistributor.java
@@ -122,7 +122,7 @@ public class SolrCmdDistributor implements Closeable {
       int maxErrorsToShow = 10;
       for (Error e:errors) {
         if (maxErrorsToShow-- <= 0) break;
-        builder.append("\n" + e);
+        builder.append("\n").append(e);
       }
       if (errors.size() > 10) {
         builder.append("\n... and ");
diff --git a/solr/core/src/java/org/apache/solr/update/SplitIndexCommand.java b/solr/core/src/java/org/apache/solr/update/SplitIndexCommand.java
index 7ea8a2ad9a3..56208a8e400 100644
--- a/solr/core/src/java/org/apache/solr/update/SplitIndexCommand.java
+++ b/solr/core/src/java/org/apache/solr/update/SplitIndexCommand.java
@@ -60,17 +60,17 @@ public class SplitIndexCommand extends UpdateCommand {
   @Override
   public String toString() {
     StringBuilder sb = new StringBuilder(super.toString());
-    sb.append(",paths=" + paths);
-    sb.append(",cores=" + cores);
-    sb.append(",ranges=" + ranges);
-    sb.append(",router=" + router);
+    sb.append(",paths=").append(paths);
+    sb.append(",cores=").append(cores);
+    sb.append(",ranges=").append(ranges);
+    sb.append(",router=").append(router);
     if (routeFieldName != null) {
-      sb.append(",routeFieldName=" + routeFieldName);
+      sb.append(",routeFieldName=").append(routeFieldName);
     }
     if (splitKey != null) {
-      sb.append(",split.key=" + splitKey);
+      sb.append(",split.key=").append(splitKey);
     }
-    sb.append(",method=" + splitMethod.toLower());
+    sb.append(",method=").append(splitMethod.toLower());
     sb.append('}');
     return sb.toString();
   }
diff --git a/solr/core/src/java/org/apache/solr/util/SimplePostTool.java b/solr/core/src/java/org/apache/solr/util/SimplePostTool.java
index fa429b84eb7..40fc2cd0610 100644
--- a/solr/core/src/java/org/apache/solr/util/SimplePostTool.java
+++ b/solr/core/src/java/org/apache/solr/util/SimplePostTool.java
@@ -1042,7 +1042,7 @@ public class SimplePostTool {
     StringBuilder sb = new StringBuilder();
     if (nodes.getLength() > 0) {
       for(int i = 0; i < nodes.getLength() ; i++) {
-        sb.append(nodes.item(i).getNodeValue() + " ");
+        sb.append(nodes.item(i).getNodeValue()).append(' ');
         if(!concatAll) break;
       }
       return sb.toString().trim();
diff --git a/solr/core/src/java/org/apache/solr/util/SolrLogLayout.java b/solr/core/src/java/org/apache/solr/util/SolrLogLayout.java
index d0bf3e9b9c1..f7c02ce364c 100644
--- a/solr/core/src/java/org/apache/solr/util/SolrLogLayout.java
+++ b/solr/core/src/java/org/apache/solr/util/SolrLogLayout.java
@@ -160,16 +160,16 @@ public class SolrLogLayout extends AbstractStringLayout {
         coreInfoMap.put(core.hashCode(), info);
         
         if (sb.length() == 0) sb.append("ASYNC ");
-        sb.append(" NEW_CORE " + info.shortId);
-        sb.append(" name=" + core.getName());
-        sb.append(" " + core);
+        sb.append(" NEW_CORE ").append(info.shortId);
+        sb.append(" name=").append(core.getName());
+        sb.append(" ").append(core);
       }
 
       zkController = core.getCoreContainer().getZkController();
       if (zkController != null) {
         if (info.url == null) {
           info.url = zkController.getBaseUrl() + "/" + core.getName();
-          sb.append(" url=" + info.url + " node=" + zkController.getNodeName());
+          sb.append(" url=").append(info.url).append(" node=").append(zkController.getNodeName());
         }
         
         Map<String,Object> coreProps = getReplicaProps(zkController, core);
@@ -179,7 +179,7 @@ public class SolrLogLayout extends AbstractStringLayout {
               + core.getCoreDescriptor().getCloudDescriptor()
                   .getCollectionName() + " core:" + core.getName() + " props:"
               + coreProps;
-          sb.append(" " + info.shortId + "_STATE=" + corePropsString);
+          sb.append(" ").append(info.shortId).append("_STATE=").append(corePropsString);
         }
       }
     }
diff --git a/solr/core/src/java/org/apache/solr/util/SolrPluginUtils.java b/solr/core/src/java/org/apache/solr/util/SolrPluginUtils.java
index 6d9ba6d87b4..02b253e1b14 100644
--- a/solr/core/src/java/org/apache/solr/util/SolrPluginUtils.java
+++ b/solr/core/src/java/org/apache/solr/util/SolrPluginUtils.java
@@ -1064,7 +1064,7 @@ public class SolrPluginUtils {
           StringBuilder builder = new StringBuilder();
           for (Map.Entry<Integer, String>entry : purposes.entrySet()) {
               if ((reqPurpose & entry.getKey()) != 0) {
-                  builder.append(entry.getValue() + ",");
+                  builder.append(entry.getValue()).append(',');
               }
           }
           if (builder.length() == 0) {
diff --git a/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/Facet2DStream.java b/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/Facet2DStream.java
index f83e2fd648e..6e3dd0a7910 100644
--- a/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/Facet2DStream.java
+++ b/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/Facet2DStream.java
@@ -350,16 +350,16 @@ public class Facet2DStream extends TupleStream implements Expressible {
     buf.append('"');
     buf.append(":{");
     buf.append("\"type\":\"terms\"");
-    buf.append(",\"field\":\"" + x.toString() + "\"");
-    buf.append(",\"limit\":" + dimensionX );
+    buf.append(",\"field\":\"").append(x.toString()).append('"');
+    buf.append(",\"limit\":").append(dimensionX);
     buf.append(",\"overrequest\":1000");
     String fsort = getFacetSort(adjustedSorts[0].getLeftFieldName(), metric);
-    buf.append(",\"sort\":\""+ fsort + " desc\"");
+    buf.append(",\"sort\":\"").append(fsort).append(" desc\"");
     buf.append(",\"facet\":{");
 
     String identifier = metric.getIdentifier();
     if (!identifier.startsWith("count(")) {
-      buf.append("\"agg\":\"" + identifier + "\"");
+      buf.append("\"agg\":\"").append(identifier).append('"');
       buf.append(",");
     }
     buf.append('"');
@@ -367,14 +367,14 @@ public class Facet2DStream extends TupleStream implements Expressible {
     buf.append('"');
     buf.append(":{");
     buf.append("\"type\":\"terms\"");
-    buf.append(",\"field\":\"" + y.toString() + "\"");
-    buf.append(",\"limit\":" + dimensionY );
+    buf.append(",\"field\":\"").append(y.toString()).append('"');
+    buf.append(",\"limit\":").append(dimensionY);
     buf.append(",\"overrequest\":1000");
     String fsortY = getFacetSort(adjustedSorts[1].getLeftFieldName(), metric);
-    buf.append(",\"sort\":\""+ fsortY + " desc\"");
+    buf.append(",\"sort\":\"").append(fsortY).append(" desc\"");
     buf.append(",\"facet\":{");
     if (!identifier.startsWith("count(")) {
-      buf.append("\"agg\":\"" + identifier + "\"");
+      buf.append("\"agg\":\"").append(identifier).append('"');
     }
     buf.append("}}}}");
   }
diff --git a/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/FacetStream.java b/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/FacetStream.java
index 38d09042b8f..9257df3435e 100644
--- a/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/FacetStream.java
+++ b/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/FacetStream.java
@@ -644,20 +644,20 @@ public class FacetStream extends TupleStream implements Expressible  {
     buf.append('"');
     buf.append(":{");
     buf.append("\"type\":\"terms\"");
-    buf.append(",\"field\":\""+_buckets[level].toString()+"\"");
-    buf.append(",\"limit\":"+_limit);
+    buf.append(",\"field\":\"").append(_buckets[level].toString()).append('"');
+    buf.append(",\"limit\":").append(_limit);
 
     if(refine) {
       buf.append(",\"refine\":true");
     }
 
     if(method != null) {
-      buf.append(",\"method\":\""+method+"\"");
+      buf.append(",\"method\":\"").append(method).append('"');
     }
 
     String fsort = getFacetSort(_sorts[level].getLeftFieldName(), _metrics);
 
-    buf.append(",\"sort\":{\""+fsort+"\":\""+_sorts[level].getOrder()+"\"}");
+    buf.append(",\"sort\":{\"").append(fsort).append("\":\"").append(_sorts[level].getOrder()).append("\"}");
 
     buf.append(",\"facet\":{");
     int metricCount = 0;
@@ -673,7 +673,7 @@ public class FacetStream extends TupleStream implements Expressible  {
           if (metricCount > 0) {
             buf.append(",");
           }
-          buf.append("\""+ facetKey + "\":\"" + identifier + "\"");
+          buf.append('"').append(facetKey).append("\":\"").append(identifier).append('"');
           ++metricCount;
         }
       }
diff --git a/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/KnnStream.java b/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/KnnStream.java
index b8fa4b84e76..64fcd027969 100644
--- a/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/KnnStream.java
+++ b/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/KnnStream.java
@@ -195,7 +195,7 @@ public class KnnStream extends TupleStream implements Expressible  {
 
     for(String key : mltParams) {
       if(params.get(key) != null) {
-        builder.append(" " + key + "=" + params.get(key));
+        builder.append(' ').append(key).append('=').append(params.get(key));
         params.remove(key);
       }
     }
diff --git a/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/TimeSeriesStream.java b/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/TimeSeriesStream.java
index 764c70bb9f3..19c886aec5c 100644
--- a/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/TimeSeriesStream.java
+++ b/solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/TimeSeriesStream.java
@@ -344,10 +344,10 @@ public class TimeSeriesStream extends TupleStream implements Expressible  {
     buf.append('"');
     buf.append(":{");
     buf.append("\"type\":\"range\"");
-    buf.append(",\"field\":\""+field+"\"");
-    buf.append(",\"start\":\""+start+"\"");
-    buf.append(",\"end\":\""+end+"\"");
-    buf.append(",\"gap\":\""+gap+"\"");
+    buf.append(",\"field\":\"").append(field).append('"');
+    buf.append(",\"start\":\"").append(start).append('"');
+    buf.append(",\"end\":\"").append(end).append('"');
+    buf.append(",\"gap\":\"").append(gap).append('"');
 
     buf.append(",\"facet\":{");
     int metricCount = 0;
@@ -357,7 +357,7 @@ public class TimeSeriesStream extends TupleStream implements Expressible  {
         if(metricCount>0) {
           buf.append(",");
         }
-        buf.append("\"facet_" + metricCount + "\":\"" +identifier+"\"");
+        buf.append("\"facet_").append(metricCount).append("\":\"").append(identifier).append('"');
         ++metricCount;
       }
     }
diff --git a/solr/solrj/src/java/org/apache/solr/client/solrj/request/UpdateRequest.java b/solr/solrj/src/java/org/apache/solr/client/solrj/request/UpdateRequest.java
index 3eb20eb3a75..902223e30d1 100644
--- a/solr/solrj/src/java/org/apache/solr/client/solrj/request/UpdateRequest.java
+++ b/solr/solrj/src/java/org/apache/solr/client/solrj/request/UpdateRequest.java
@@ -486,7 +486,7 @@ public class UpdateRequest extends AbstractUpdateRequest {
     boolean deleteQ = deleteQuery != null && deleteQuery.size() > 0;
     if (deleteI || deleteQ) {
       if (commitWithin > 0) {
-        writer.append("<delete commitWithin=\"" + commitWithin + "\">");
+        writer.append("<delete commitWithin=\"").append(String.valueOf(commitWithin)).append("\">");
       } else {
         writer.append("<delete>");
       }
@@ -498,11 +498,11 @@ public class UpdateRequest extends AbstractUpdateRequest {
             Long version = (Long) map.get(VER);
             String route = (String)map.get(_ROUTE_);
             if (version != null) {
-              writer.append(" version=\"" + version + "\"");
+              writer.append(" version=\"").append(String.valueOf(version)).append('"');
             }
             
             if (route != null) {
-              writer.append(" _route_=\"" + route + "\"");
+              writer.append(" _route_=\"").append(route).append('"');
             }
           }
           writer.append(">");
diff --git a/solr/solrj/src/java/org/apache/solr/common/cloud/ClusterState.java b/solr/solrj/src/java/org/apache/solr/common/cloud/ClusterState.java
index 9907b9cbae3..559203f6137 100644
--- a/solr/solrj/src/java/org/apache/solr/common/cloud/ClusterState.java
+++ b/solr/solrj/src/java/org/apache/solr/common/cloud/ClusterState.java
@@ -214,11 +214,11 @@ public class ClusterState implements JSONWriter.Writable {
   @Override
   public String toString() {
     StringBuilder sb = new StringBuilder();
-    sb.append("znodeVersion: " + znodeVersion);
+    sb.append("znodeVersion: ").append(znodeVersion);
     sb.append("\n");
-    sb.append("live nodes:" + liveNodes);
+    sb.append("live nodes:").append(liveNodes);
     sb.append("\n");
-    sb.append("collections:" + collectionStates);
+    sb.append("collections:").append(collectionStates);
     return sb.toString();
   }
 
diff --git a/solr/solrj/src/java/org/apache/solr/common/cloud/SolrZkClient.java b/solr/solrj/src/java/org/apache/solr/common/cloud/SolrZkClient.java
index ff5797c8ad7..98f0d9ad0bd 100644
--- a/solr/solrj/src/java/org/apache/solr/common/cloud/SolrZkClient.java
+++ b/solr/solrj/src/java/org/apache/solr/common/cloud/SolrZkClient.java
@@ -503,7 +503,7 @@ public class SolrZkClient implements Closeable {
     StringBuilder sbPath = new StringBuilder();
     for (int i = 0; i < paths.length; i++) {
       String pathPiece = paths[i];
-      sbPath.append("/" + pathPiece);
+      sbPath.append("/").append(pathPiece);
       if (i < skipPathParts) {
         continue;
       }
@@ -597,7 +597,7 @@ public class SolrZkClient implements Closeable {
     for (int i = 0; i < indent; i++) {
       dent.append(" ");
     }
-    string.append(dent + path + " (" + children.size() + ")" + NEWL);
+    string.append(dent).append(path).append(" (").append(children.size()).append(")").append(NEWL);
     if (data != null) {
       String dataString = new String(data, StandardCharsets.UTF_8);
       if ((!path.endsWith(".txt") && !path.endsWith(".xml")) || path.endsWith(ZkStateReader.CLUSTER_STATE)) {
@@ -606,10 +606,9 @@ public class SolrZkClient implements Closeable {
           dataString = prettyPrint(dataString);
         }
 
-        string.append(dent + "DATA:\n" + dent + "    "
-            + dataString.replaceAll("\n", "\n" + dent + "    ") + NEWL);
+        string.append(dent).append("DATA:\n").append(dent).append("    ").append(dataString.replaceAll("\n", "\n" + dent + "    ")).append(NEWL);
       } else {
-        string.append(dent + "DATA: ...supressed..." + NEWL);
+        string.append(dent).append("DATA: ...supressed...").append(NEWL);
       }
     }
 
diff --git a/solr/solrj/src/java/org/apache/solr/common/util/ExecutorUtil.java b/solr/solrj/src/java/org/apache/solr/common/util/ExecutorUtil.java
index 6082a690b34..a053a180109 100644
--- a/solr/solrj/src/java/org/apache/solr/common/util/ExecutorUtil.java
+++ b/solr/solrj/src/java/org/apache/solr/common/util/ExecutorUtil.java
@@ -172,7 +172,7 @@ public class ExecutorUtil {
         Collection<String> values = submitterContext.values();
 
         for (String value : values) {
-          contextString.append(value + " ");
+          contextString.append(value).append(' ');
         }
         if (contextString.length() > 1) {
           contextString.setLength(contextString.length() - 1);
diff --git a/solr/test-framework/src/java/org/apache/solr/cloud/AbstractFullDistribZkTestBase.java b/solr/test-framework/src/java/org/apache/solr/cloud/AbstractFullDistribZkTestBase.java
index 71658cc70a1..cdb6f68a1b4 100644
--- a/solr/test-framework/src/java/org/apache/solr/cloud/AbstractFullDistribZkTestBase.java
+++ b/solr/test-framework/src/java/org/apache/solr/cloud/AbstractFullDistribZkTestBase.java
@@ -899,7 +899,7 @@ public abstract class AbstractFullDistribZkTestBase extends AbstractDistribZkTes
       StringBuilder sb = new StringBuilder();
       for (int i = 0; i < sliceCount; i++) {
         if (i > 0) sb.append(',');
-        sb.append("shard" + (i + 1));
+        sb.append("shard").append(i + 1);
       }
       params.set("shards", sb.toString());
     }
diff --git a/solr/test-framework/src/java/org/apache/solr/cloud/ChaosMonkey.java b/solr/test-framework/src/java/org/apache/solr/cloud/ChaosMonkey.java
index 3b883e0d18f..a6939b225ee 100644
--- a/solr/test-framework/src/java/org/apache/solr/cloud/ChaosMonkey.java
+++ b/solr/test-framework/src/java/org/apache/solr/cloud/ChaosMonkey.java
@@ -653,7 +653,7 @@ public class ChaosMonkey {
     StringBuilder builder = new StringBuilder();
     builder.append("Collection status: {");
     for (Slice slice:docCollection.getSlices()) {
-      builder.append(slice.getName() + ": {");
+      builder.append(slice.getName()).append(": {");
       for (Replica replica:slice.getReplicas()) {
         log.info(replica.toString());
         java.util.regex.Matcher m = portPattern.matcher(replica.getBaseUrl());