StringBuffer -> StringBuilder

My use case does not require thread-safety.

Change-Id: Ibb4d639c2980ede301577ab1e39958f5856444c7
diff --git a/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZClient.java b/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZClient.java
index 4b6e8a1..f45483c 100644
--- a/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZClient.java
+++ b/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZClient.java
@@ -342,9 +342,9 @@
     }
 
     private String getCounterName(final IKVTableID tableId, final byte[] key) {
-        StringBuffer buf = new StringBuffer(tableId.getTableName());
+        StringBuilder buf = new StringBuilder(tableId.getTableName());
         buf.append('@');
-        ByteArrayUtil.toHexStringBuffer(key, ":", buf);
+        ByteArrayUtil.toHexStringBuilder(key, ":", buf);
         return buf.toString();
     }
 
diff --git a/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZMultiEntryOperation.java b/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZMultiEntryOperation.java
index 99db3cc..58df13b 100644
--- a/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZMultiEntryOperation.java
+++ b/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZMultiEntryOperation.java
@@ -161,7 +161,7 @@
     @Override
     public String toString() {
         return "[HZMultiEntryOperation table=" + table + ", key="
-                + ByteArrayUtil.toHexStringBuffer(key, ":") + ", operation=" + operation
+                + ByteArrayUtil.toHexStringBuilder(key, ":") + ", operation=" + operation
                 + ", status=" + status + ", writeValue=" + writeValue + "]";
     }
 }