diff -r 6af860e04527 -r eb4fcf73ee99 jdk/src/share/classes/javax/swing/text/JTextComponent.java
--- a/jdk/src/share/classes/javax/swing/text/JTextComponent.java	Tue Nov 02 15:08:56 2010 +0900
+++ b/jdk/src/share/classes/javax/swing/text/JTextComponent.java	Tue Nov 02 13:32:00 2010 +0300
@@ -35,10 +35,7 @@
 import java.util.Hashtable;
 import java.util.Enumeration;
 import java.util.Vector;
-import java.util.Iterator;
 import java.util.Map;
-import java.util.Map.Entry;
-import java.util.Set;
 
 import java.util.concurrent.*;
 
@@ -4058,7 +4055,7 @@
 
     private static final Object KEYMAP_TABLE =
         new StringBuilder("JTextComponent_KeymapTable");
-    private JTextComponent editor;
+
     //
     // member variables used for on-the-spot input method
     // editing style support
@@ -4748,14 +4745,14 @@
                         processKeyEvent(ke);
                     }
                 } else {
-                    StringBuffer strBuf = new StringBuffer();
+                    StringBuilder strBuf = new StringBuilder();
                     for (char c = text.current(); commitCount > 0;
                          c = text.next(), commitCount--) {
                         strBuf.append(c);
                     }
 
                     // map it to an ActionEvent
-                    mapCommittedTextToAction(new String(strBuf));
+                    mapCommittedTextToAction(strBuf.toString());
                 }
 
                 // Remember latest committed text end index
@@ -4801,7 +4798,7 @@
     private void createComposedTextAttribute(int composedIndex,
                                         AttributedCharacterIterator text) {
         Document doc = getDocument();
-        StringBuffer strBuf = new StringBuffer();
+        StringBuilder strBuf = new StringBuilder();
 
         // create attributed string with no attributes
         for (char c = text.setIndex(composedIndex);
@@ -4809,7 +4806,7 @@
             strBuf.append(c);
         }
 
-        composedTextContent = new String(strBuf);
+        composedTextContent = strBuf.toString();
         composedTextAttribute = new SimpleAttributeSet();
         composedTextAttribute.addAttribute(StyleConstants.ComposedTextAttribute,
                 new AttributedString(text, composedIndex, text.getEndIndex()));