diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U16.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U16.java
index 9de7e14..6c4ac11 100644
--- a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U16.java
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U16.java
@@ -63,7 +63,7 @@
 
     @Override
     public String toString() {
-        return Integer.toString(f(raw));
+        return String.format("0x%04x", raw);
     }
 
     @Override
diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U32.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U32.java
index 7f53374..c69786c 100644
--- a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U32.java
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U32.java
@@ -61,7 +61,7 @@
 
     @Override
     public String toString() {
-        return "" + f(raw);
+        return String.format("0x%08x", raw);
     }
 
     @Override
diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U64.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U64.java
index 9001eb8..dea6e6d 100644
--- a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U64.java
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U64.java
@@ -66,7 +66,7 @@
 
     @Override
     public String toString() {
-        return getBigInteger().toString();
+        return String.format("0x%016x", raw);
     }
 
     public static BigInteger f(final long value) {
diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U8.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U8.java
index c644599..17191af 100644
--- a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U8.java
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U8.java
@@ -62,7 +62,7 @@
 
     @Override
     public String toString() {
-        return "" + f(raw);
+        return String.format("0x%02x", raw);
     }
 
     @Override