diff --git a/TracerOnJavassist/src/tracer/JSONArrayAdvisor.java b/TracerOnJavassist/src/tracer/JSONArrayAdvisor.java
index 3608896..8bcbe47 100644
--- a/TracerOnJavassist/src/tracer/JSONArrayAdvisor.java
+++ b/TracerOnJavassist/src/tracer/JSONArrayAdvisor.java
@@ -116,7 +116,8 @@
 	public static void arrayWriteObject(Object array, int index, Object value) {
 		long threadId = Thread.currentThread().getId();
 		long timeStamp = System.nanoTime();
-		JSONTraceGenerator.arraySetOutput(array.getClass().getName(), Integer.toString(System.identityHashCode(array)), index, value.getClass().getName(), Integer.toString(System.identityHashCode(value)), threadId, timeStamp);
+		JSONTraceGenerator.arraySetOutput(array.getClass().getName(), Integer.toString(System.identityHashCode(array)), index, 
+				((value !=null)?value.getClass().getName():"---"), ((value != null)?Integer.toString(System.identityHashCode(value)):"0"), threadId, timeStamp);
 		((Object [])array)[index] = value;
 	}
 
@@ -124,7 +125,8 @@
 		Object value = ((Object [])array)[index];
 		long threadId = Thread.currentThread().getId();
 		long timeStamp = System.nanoTime();
-		JSONTraceGenerator.arrayGetOutput(array.getClass().getName(), Integer.toString(System.identityHashCode(array)), index, value.getClass().getName(), Integer.toString(System.identityHashCode(value)), threadId, timeStamp);
+		JSONTraceGenerator.arrayGetOutput(array.getClass().getName(), Integer.toString(System.identityHashCode(array)), index, 
+				((value !=null)?value.getClass().getName():"---"), ((value != null)?Integer.toString(System.identityHashCode(value)):"0"), threadId, timeStamp);
 		return value;
 	}
 }