diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 8d12d0fddec..d7c3e846612 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -69,6 +69,10 @@ 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 9ef31e81428..76bbcfae089 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 d6b50f3de63..4dea8850d2a 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 123d5290f10..1a72a73d8b4 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 2e99a0666d8..6b5a7d752f8 100644
--- a/lucene/sandbox/src/java/org/apache/lucene/search/TermAutomatonQuery.java
+++ b/lucene/sandbox/src/java/org/apache/lucene/search/TermAutomatonQuery.java
@@ -285,9 +285,9 @@ 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 2c453d71998..a035a9904f8 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
@@ -1285,8 +1285,8 @@ 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 aadfc88ba22..0577d834cc7 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
@@ -119,14 +119,14 @@ 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 a1d71a5191b..1b0cfcf21f1 100644
--- a/solr/core/src/java/org/apache/solr/util/SimplePostTool.java
+++ b/solr/core/src/java/org/apache/solr/util/SimplePostTool.java
@@ -1043,7 +1043,7 @@ 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 0611ca53d28..3d22d13e2a3 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());