diff --git a/core/src/main/java/hudson/MarkupText.java b/core/src/main/java/hudson/MarkupText.java
index 03ef1fcb02..1274ccb8a2 100644
--- a/core/src/main/java/hudson/MarkupText.java
+++ b/core/src/main/java/hudson/MarkupText.java
@@ -193,7 +193,7 @@ public class MarkupText extends AbstractMarkupText {
          * Replaces the group tokens like "$0", "$1", and etc with their actual matches.
          */
         public String replace(String s) {
-            StringBuffer buf = new StringBuffer();
+            StringBuilder buf = new StringBuilder(s.length() + 10);
 
             for( int i=0; i<s.length(); i++) {
                 char ch = s.charAt(i);
diff --git a/core/src/main/java/hudson/util/QuotedStringTokenizer.java b/core/src/main/java/hudson/util/QuotedStringTokenizer.java
index 6c22572602..e917c92b4d 100644
--- a/core/src/main/java/hudson/util/QuotedStringTokenizer.java
+++ b/core/src/main/java/hudson/util/QuotedStringTokenizer.java
@@ -441,58 +441,55 @@ public class QuotedStringTokenizer
         if (first!=last || (first!='"' && first!='\''))
             return s;
 
-        StringBuffer b=new StringBuffer(s.length()-2);
-        synchronized(b)
+        StringBuilder b=new StringBuilder(s.length()-2);
+        boolean escape=false;
+        for (int i=1;i<s.length()-1;i++)
         {
-            boolean escape=false;
-            for (int i=1;i<s.length()-1;i++)
+            char c = s.charAt(i);
+
+            if (escape)
             {
-                char c = s.charAt(i);
-
-                if (escape)
+                escape=false;
+                switch (c)
                 {
-                    escape=false;
-                    switch (c)
-                    {
-                        case 'n':
-                            b.append('\n');
-                            break;
-                        case 'r':
-                            b.append('\r');
-                            break;
-                        case 't':
-                            b.append('\t');
-                            break;
-                        case 'f':
-                            b.append('\f');
-                            break;
-                        case 'b':
-                            b.append('\b');
-                            break;
-                        case 'u':
-                            b.append((char)(
-                                    (convertHexDigit((byte)s.charAt(i++))<<24)+
-                                    (convertHexDigit((byte)s.charAt(i++))<<16)+
-                                    (convertHexDigit((byte)s.charAt(i++))<<8)+
-                                    (convertHexDigit((byte)s.charAt(i++)))
-                                    )
-                            );
-                            break;
-                        default:
-                            b.append(c);
-                    }
+                    case 'n':
+                        b.append('\n');
+                        break;
+                    case 'r':
+                        b.append('\r');
+                        break;
+                    case 't':
+                        b.append('\t');
+                        break;
+                    case 'f':
+                        b.append('\f');
+                        break;
+                    case 'b':
+                        b.append('\b');
+                        break;
+                    case 'u':
+                        b.append((char)(
+                                (convertHexDigit((byte)s.charAt(i++))<<24)+
+                                (convertHexDigit((byte)s.charAt(i++))<<16)+
+                                (convertHexDigit((byte)s.charAt(i++))<<8)+
+                                (convertHexDigit((byte)s.charAt(i++)))
+                                )
+                        );
+                        break;
+                    default:
+                        b.append(c);
                 }
-                else if (c=='\\')
-                {
-                    escape=true;
-                    continue;
-                }
-                else
-                    b.append(c);
             }
-
-            return b.toString();
+            else if (c=='\\')
+            {
+                escape=true;
+                continue;
+            }
+            else
+                b.append(c);
         }
+
+        return b.toString();
     }
 
     /* ------------------------------------------------------------ */
diff --git a/core/src/main/java/hudson/util/VersionNumber.java b/core/src/main/java/hudson/util/VersionNumber.java
index ce65bd39c3..844e82d0fa 100644
--- a/core/src/main/java/hudson/util/VersionNumber.java
+++ b/core/src/main/java/hudson/util/VersionNumber.java
@@ -105,7 +105,7 @@ public class VersionNumber implements Comparable<VersionNumber> {
 
     @Override
     public String toString() {
-        StringBuffer buf = new StringBuffer();
+        StringBuilder buf = new StringBuilder();
         for( int i=0; i<digits.length; i++ ) {
             if(i!=0)    buf.append('.');
             buf.append( Integer.toString(digits[i]) );