diff --git a/src/main/com/mongodb/ByteEncoder.java b/src/main/com/mongodb/ByteEncoder.java
index 7b9684e..23bb8d4 100644
--- a/src/main/com/mongodb/ByteEncoder.java
+++ b/src/main/com/mongodb/ByteEncoder.java
@@ -498,7 +507,7 @@ public class ByteEncoder extends Bytes {
             sm.put(options.charAt(i), options.charAt(i));
         }
 
-        StringBuffer sb = new StringBuffer();
+        StringBuilder sb = new StringBuilder();
 
         for (char c : sm.keySet()) {
             sb.append(c);
diff --git a/src/main/com/mongodb/util/CustomHashMap.java b/src/main/com/mongodb/util/CustomHashMap.java
index 812ff89..e34bc6b 100644
--- a/src/main/com/mongodb/util/CustomHashMap.java
+++ b/src/main/com/mongodb/util/CustomHashMap.java
@@ -1040,7 +1048,7 @@ public abstract class CustomHashMap<K,V> implements Map<K,V> , Cloneable , Seria
      * @return a String representation of this map.
      */
     public String toString() {
-	StringBuffer buf = new StringBuffer();
+	StringBuilder buf = new StringBuilder();
 	buf.append("{");
 
 	Iterator<Map.Entry<K,V>> i = entrySet().iterator();
diff --git a/src/main/com/mongodb/util/JSON.java b/src/main/com/mongodb/util/JSON.java
index 04ce550..4a2482e 100644
--- a/src/main/com/mongodb/util/JSON.java
+++ b/src/main/com/mongodb/util/JSON.java
@@ -389,7 +399,7 @@ class JSONParser {
         char current;
 
         read(quot);
-        StringBuffer buf = new StringBuffer();
+        StringBuilder buf = new StringBuilder();
         int start = pos;
         while(pos < s.length() && 
               (current = s.charAt(pos)) != quot) {
@@ -550,7 +560,7 @@ class JSONParseException extends RuntimeException {
     int pos;
 
     public String getMessage() {
-        StringBuffer sb = new StringBuffer();
+        StringBuilder sb = new StringBuilder();
         sb.append("\n");
         sb.append(s);
         sb.append("\n");
diff --git a/src/main/com/mongodb/util/Util.java b/src/main/com/mongodb/util/Util.java
index 8f76162..3ef46ce 100644
--- a/src/main/com/mongodb/util/Util.java
+++ b/src/main/com/mongodb/util/Util.java
@@ -25,7 +25,7 @@ import java.security.NoSuchAlgorithmException;
 public class Util {
 
     public static String toHex( byte b[] ){
-        StringBuffer sb = new StringBuffer();
+    	 StringBuilder sb = new StringBuilder();
         
         for ( int i=0; i<b.length; i++ ){
             String s = Integer.toHexString(0xff & b[i]);