diff --git a/src/examples/src/org/apache/poi/poifs/poibrowser/PropertySetDescriptorRenderer.java b/src/examples/src/org/apache/poi/poifs/poibrowser/PropertySetDescriptorRenderer.java
index e6e55c0a27..153dc5e205 100644
--- a/src/examples/src/org/apache/poi/poifs/poibrowser/PropertySetDescriptorRenderer.java
+++ b/src/examples/src/org/apache/poi/poifs/poibrowser/PropertySetDescriptorRenderer.java
@@ -108,7 +108,7 @@ public class PropertySetDescriptorRenderer extends DocumentDescriptorRenderer
      */
     protected String sectionsToString(final List<Section> sections)
     {
-        final StringBuffer b = new StringBuffer();
+        final StringBuilder b = new StringBuilder();
         int count = 1;
         for (Iterator<Section>  i = sections.iterator(); i.hasNext();)
         {
@@ -129,7 +129,7 @@ public class PropertySetDescriptorRenderer extends DocumentDescriptorRenderer
      */
     protected String toString(final Section s, final String name)
     {
-        final StringBuffer b = new StringBuffer();
+        final StringBuilder b = new StringBuilder();
         b.append("\n" + name + " Format ID: ");
         b.append(HexDump.toHex(s.getFormatID().getBytes()));
         b.append("\n" + name + " Offset: " + s.getOffset());
diff --git a/src/java/org/apache/poi/hssf/extractor/EventBasedExcelExtractor.java b/src/java/org/apache/poi/hssf/extractor/EventBasedExcelExtractor.java
index e49a66b2fe..11f2d46369 100644
--- a/src/java/org/apache/poi/hssf/extractor/EventBasedExcelExtractor.java
+++ b/src/java/org/apache/poi/hssf/extractor/EventBasedExcelExtractor.java
@@ -162,7 +162,7 @@ public class EventBasedExcelExtractor extends POIOLE2TextExtractor implements or
        private SSTRecord sstRecord;
 
        private final List<String> sheetNames;
-       final StringBuffer _text = new StringBuffer();
+       final StringBuilder _text = new StringBuilder();
        private int sheetNum = -1;
        private int rowNum;
 
diff --git a/src/java/org/apache/poi/hssf/model/InternalSheet.java b/src/java/org/apache/poi/hssf/model/InternalSheet.java
index 4e8798e886..1b2531aee7 100644
--- a/src/java/org/apache/poi/hssf/model/InternalSheet.java
+++ b/src/java/org/apache/poi/hssf/model/InternalSheet.java
@@ -553,7 +553,7 @@ public final class InternalSheet {
         {
             log.log(POILogger.DEBUG, "Sheet.setDimensions");
             log.log(POILogger.DEBUG,
-                    (new StringBuffer("firstrow")).append(firstrow)
+                    (new StringBuilder("firstrow")).append(firstrow)
                         .append("firstcol").append(firstcol).append("lastrow")
                         .append(lastrow).append("lastcol").append(lastcol)
                         .toString());
diff --git a/src/java/org/apache/poi/hssf/record/MergeCellsRecord.java b/src/java/org/apache/poi/hssf/record/MergeCellsRecord.java
index d1e5121154..c71cbb2b66 100644
--- a/src/java/org/apache/poi/hssf/record/MergeCellsRecord.java
+++ b/src/java/org/apache/poi/hssf/record/MergeCellsRecord.java
@@ -90,7 +90,7 @@ public final class MergeCellsRecord extends StandardRecord implements Cloneable
 
     @Override
     public String toString() {
-        StringBuffer retval = new StringBuffer();
+        StringBuilder retval = new StringBuilder();
 
         retval.append("[MERGEDCELLS]").append("\n");
         retval.append("     .numregions =").append(getNumAreas()).append("\n");
diff --git a/src/java/org/apache/poi/hssf/record/pivottable/PageItemRecord.java b/src/java/org/apache/poi/hssf/record/pivottable/PageItemRecord.java
index a41d2ca031..8d8a059cd4 100644
--- a/src/java/org/apache/poi/hssf/record/pivottable/PageItemRecord.java
+++ b/src/java/org/apache/poi/hssf/record/pivottable/PageItemRecord.java
@@ -52,7 +52,7 @@ public final class PageItemRecord extends StandardRecord {
 			out.writeShort(_idObj);
 		}
 
-		public void appendDebugInfo(StringBuffer sb) {
+		public void appendDebugInfo(StringBuilder sb) {
 			sb.append('(');
 			sb.append( "isxvi=").append(HexDump.shortToHex(_isxvi));
 			sb.append(" isxvd=").append(HexDump.shortToHex(_isxvd));
@@ -97,7 +97,7 @@ public final class PageItemRecord extends StandardRecord {
 
 	@Override
 	public String toString() {
-		StringBuffer sb = new StringBuffer();
+		StringBuilder sb = new StringBuilder();
 
 		sb.append("[SXPI]\n");
 		for (int i = 0; i < _fieldInfos.length; i++) {
diff --git a/src/java/org/apache/poi/hssf/usermodel/FontDetails.java b/src/java/org/apache/poi/hssf/usermodel/FontDetails.java
index d40ec07fcd..d9fc1d54c2 100644
--- a/src/java/org/apache/poi/hssf/usermodel/FontDetails.java
+++ b/src/java/org/apache/poi/hssf/usermodel/FontDetails.java
@@ -156,7 +156,7 @@ public class FontDetails
         {
             if(max != -1 && i == listSize - 1)
             {
-                StringBuffer buf = new StringBuffer((text.length() * (listSize - i)) / listSize);
+                StringBuilder buf = new StringBuilder((text.length() * (listSize - i)) / listSize);
                 while(tok.hasMoreTokens())
                 {
                     buf.append(tok.nextToken());
diff --git a/src/java/org/apache/poi/ss/formula/CellEvaluationFrame.java b/src/java/org/apache/poi/ss/formula/CellEvaluationFrame.java
index 46ab79b10f..b9c7efc678 100644
--- a/src/java/org/apache/poi/ss/formula/CellEvaluationFrame.java
+++ b/src/java/org/apache/poi/ss/formula/CellEvaluationFrame.java
@@ -40,7 +40,7 @@ final class CellEvaluationFrame {
 	}
 
 	public String toString() {
-		StringBuffer sb = new StringBuffer(64);
+		StringBuilder sb = new StringBuilder(64);
 		sb.append(getClass().getName()).append(" [");
 		sb.append("]");
 		return sb.toString();
diff --git a/src/java/org/apache/poi/ss/formula/FormulaUsedBlankCellSet.java b/src/java/org/apache/poi/ss/formula/FormulaUsedBlankCellSet.java
index 0bb94659ee..005c91dfac 100644
--- a/src/java/org/apache/poi/ss/formula/FormulaUsedBlankCellSet.java
+++ b/src/java/org/apache/poi/ss/formula/FormulaUsedBlankCellSet.java
@@ -158,7 +158,7 @@ final class FormulaUsedBlankCellSet {
 		}
 		@Override
         public String toString() {
-			StringBuffer sb = new StringBuffer(64);
+			StringBuilder sb = new StringBuilder(64);
 			CellReference crA = new CellReference(_firstRowIndex, _firstColumnIndex, false, false);
 			CellReference crB = new CellReference(_lastRowIndex, _lastColumnIndex, false, false);
 			sb.append(getClass().getName());
diff --git a/src/java/org/apache/poi/ss/formula/constant/ErrorConstant.java b/src/java/org/apache/poi/ss/formula/constant/ErrorConstant.java
index 79dd23b92a..b39c322331 100644
--- a/src/java/org/apache/poi/ss/formula/constant/ErrorConstant.java
+++ b/src/java/org/apache/poi/ss/formula/constant/ErrorConstant.java
@@ -71,7 +71,7 @@ public class ErrorConstant {
 	}
 
 	public String toString() {
-		StringBuffer sb = new StringBuffer(64);
+		StringBuilder sb = new StringBuilder(64);
 		sb.append(getClass().getName()).append(" [");
 		sb.append(getText());
 		sb.append("]");
diff --git a/src/java/org/apache/poi/util/HexRead.java b/src/java/org/apache/poi/util/HexRead.java
index 0acaef6e27..a7bec002f9 100644
--- a/src/java/org/apache/poi/util/HexRead.java
+++ b/src/java/org/apache/poi/util/HexRead.java
@@ -55,7 +55,7 @@ public class HexRead {
      */
     public static byte[] readData(InputStream stream, String section ) throws IOException {
         try {
-            StringBuffer sectionText = new StringBuffer();
+            StringBuilder sectionText = new StringBuilder();
             boolean inSection = false;
             int c = stream.read();
             while ( c != -1 ) {
@@ -66,12 +66,12 @@ public class HexRead {
                     case '\n':
                     case '\r':
                         inSection = false;
-                        sectionText = new StringBuffer();
+                        sectionText = new StringBuilder();
                         break;
                     case ']':
                         inSection = false;
                         if ( sectionText.toString().equals( section ) ) return readData( stream, '[' );
-                        sectionText = new StringBuffer();
+                        sectionText = new StringBuilder();
                         break;
                     default:
                         if ( inSection ) sectionText.append( (char) c );
diff --git a/src/scratchpad/src/org/apache/poi/hpbf/extractor/PublisherTextExtractor.java b/src/scratchpad/src/org/apache/poi/hpbf/extractor/PublisherTextExtractor.java
index ec1dc82b75..27f62aeeec 100644
--- a/src/scratchpad/src/org/apache/poi/hpbf/extractor/PublisherTextExtractor.java
+++ b/src/scratchpad/src/org/apache/poi/hpbf/extractor/PublisherTextExtractor.java
@@ -61,7 +61,7 @@ public final class PublisherTextExtractor extends POIOLE2TextExtractor {
 
 
 	public String getText() {
-		StringBuffer text = new StringBuffer();
+		StringBuilder text = new StringBuilder();
 
 		// Get the text from the Quill Contents
 		QCBit[] bits = doc.getQuillContents().getBits();
diff --git a/src/scratchpad/src/org/apache/poi/hslf/record/StyleTextPropAtom.java b/src/scratchpad/src/org/apache/poi/hslf/record/StyleTextPropAtom.java
index 372c52d9ad..c0d13c0e64 100644
--- a/src/scratchpad/src/org/apache/poi/hslf/record/StyleTextPropAtom.java
+++ b/src/scratchpad/src/org/apache/poi/hslf/record/StyleTextPropAtom.java
@@ -369,13 +369,11 @@ public final class StyleTextPropAtom extends RecordAtom {
 
 
     /**
-     * Dump the record content into <code>StringBuffer</code>
-     *
      * @return the string representation of the record data
      */
     @Override
     public String toString(){
-        StringBuffer out = new StringBuffer();
+        StringBuilder out = new StringBuilder();
 
         out.append("StyleTextPropAtom:\n");
         if (!initialised) {
diff --git a/src/testcases/org/apache/poi/hssf/usermodel/TestBugs.java b/src/testcases/org/apache/poi/hssf/usermodel/TestBugs.java
index 9d9c277def..46056ff82e 100644
--- a/src/testcases/org/apache/poi/hssf/usermodel/TestBugs.java
+++ b/src/testcases/org/apache/poi/hssf/usermodel/TestBugs.java
@@ -359,16 +359,6 @@ public final class TestBugs extends BaseTestBugzillaIssues {
         assertEquals(a.getRichStringCellValue().getString(), b.getRichStringCellValue().getString());
     }
 
-    /*private static String unicodeString(HSSFCell cell) {
-        String ss = cell.getRichStringCellValue().getString();
-        char s[] = ss.toCharArray();
-        StringBuffer sb = new StringBuffer();
-        for (int x=0;x<s.length;x++) {
-            sb.append("\\u").append(Integer.toHexString(s[x]));
-        }
-        return sb.toString();
-    }*/
-
     /**
      * Error in opening wb
      */
diff --git a/src/testcases/org/apache/poi/ss/formula/function/ExcelFileFormatDocFunctionExtractor.java b/src/testcases/org/apache/poi/ss/formula/function/ExcelFileFormatDocFunctionExtractor.java
index fe868dbdd9..ac2551665d 100644
--- a/src/testcases/org/apache/poi/ss/formula/function/ExcelFileFormatDocFunctionExtractor.java
+++ b/src/testcases/org/apache/poi/ss/formula/function/ExcelFileFormatDocFunctionExtractor.java
@@ -111,7 +111,7 @@ public final class ExcelFileFormatDocFunctionExtractor {
 			_isVolatile = isVolatile;
 		}
 		private static String convertSpecialChars(String ss) {
-			StringBuffer sb = new StringBuffer(ss.length() + 4);
+			StringBuilder sb = new StringBuilder(ss.length() + 4);
 			for(int i=0; i<ss.length(); i++) {
 				char c = ss.charAt(i);
 				if (isSimpleAscii(c)) {
@@ -256,7 +256,7 @@ public final class ExcelFileFormatDocFunctionExtractor {
 		private boolean _isInsideTable;
 
 		private final List<String> _rowData;
-		private final StringBuffer _textNodeBuffer;
+		private final StringBuilder _textNodeBuffer;
 		private final List<Boolean> _rowNoteFlags;
 		private boolean _cellHasNote;
 
@@ -268,7 +268,7 @@ public final class ExcelFileFormatDocFunctionExtractor {
 			_elemNameStack = new Stack<>();
 			_isInsideTable = false;
 			_rowData = new ArrayList<>();
-			_textNodeBuffer = new StringBuffer();
+			_textNodeBuffer = new StringBuilder();
 			_rowNoteFlags = new ArrayList<>();
 		}