diff --git a/src/main/java/net/onrc/onos/ofcontroller/util/DataPath.java b/src/main/java/net/onrc/onos/ofcontroller/util/DataPath.java
index dec70e3..e807b56 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/util/DataPath.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/util/DataPath.java
@@ -116,19 +116,18 @@
      * inPort/dpid/outPort;inPort/dpid/outPort;...
      */
     public String dataPathSummary() {
-	String resultStr = new String();
+	StringBuilder resultStr = new StringBuilder(5+1+20+1+5+1);
 	if (this.flowEntries != null) {
 	    for (FlowEntry flowEntry : this.flowEntries) {
 		// The data path summary string
-		resultStr = resultStr +
-		    flowEntry.inPort().toString() + "/"
-		    + flowEntry.dpid().toString() + "/" +
-		    flowEntry.outPort().toString() + ";";
+		resultStr.append(flowEntry.inPort().toString()).append('/')
+			.append(flowEntry.dpid().toString()).append('/')
+			.append(flowEntry.outPort().toString()).append(';');
 	    }
 	}
-	if (resultStr.isEmpty())
-	    resultStr = "X";		// Invalid shortest-path
-	return resultStr;
+	if (resultStr.length() == 0)
+	    resultStr.append("X");		// Invalid shortest-path
+	return resultStr.toString();
     }
 
     /**
diff --git a/src/main/java/org/openflow/util/HexString.java b/src/main/java/org/openflow/util/HexString.java
index 5777612..07cc1f7 100644
--- a/src/main/java/org/openflow/util/HexString.java
+++ b/src/main/java/org/openflow/util/HexString.java
@@ -27,35 +27,35 @@
      */
     public static String toHexString(byte[] bytes) {
         int i;
-        String ret = "";
+        StringBuilder ret = new StringBuilder(8*2+7);
         String tmp;
         for(i=0; i< bytes.length; i++) {
             if(i> 0)
-                ret += ":";
+                ret.append(':');
             tmp = Integer.toHexString(U8.f(bytes[i]));
             if (tmp.length() == 1)
-                ret += "0";
-            ret += tmp; 
+                ret.append('0');
+            ret.append(tmp);
         }
-        return ret;
+        return ret.toString();
     }
     
     public static String toHexString(long val, int padTo) {
         char arr[] = Long.toHexString(val).toCharArray();
-        String ret = "";
+        StringBuilder ret = new StringBuilder(8*2+7);
         // prepend the right number of leading zeros
         int i = 0;
         for (; i < (padTo * 2 - arr.length); i++) {
-            ret += "0";
+            ret.append('0');
             if ((i % 2) == 1)
-                ret += ":";
+                ret.append(':');
         }
         for (int j = 0; j < arr.length; j++) {
-            ret += arr[j];
+            ret.append(arr[j]);
             if ((((i + j) % 2) == 1) && (j < (arr.length - 1)))
-                ret += ":";
+                ret.append(':');
         }
-        return ret;        
+        return ret.toString();
     }
    
     public static String toHexString(long val) {