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;
 	}
 }
diff --git a/TracerOnJavassist/src/tracer/OutputStatementsGenerator.java b/TracerOnJavassist/src/tracer/OutputStatementsGenerator.java
index 12ef3d2..4f28a5c 100644
--- a/TracerOnJavassist/src/tracer/OutputStatementsGenerator.java
+++ b/TracerOnJavassist/src/tracer/OutputStatementsGenerator.java
@@ -169,8 +169,8 @@
 		ArrayList<String> argObjects = new ArrayList<>();
 		for (CtClass c : parameterClasses) {
 			if (!c.isPrimitive()) {
-				argClasses.add("($" + (p + 1) + ").getClass().getName()");
-				argObjects.add("System.identityHashCode($" + (p + 1) + ")");
+				argClasses.add("(($" + (p + 1) + " != null)?($" + (p + 1) + ").getClass().getName():\"" + c.getName() + "\")");
+				argObjects.add("(($" + (p + 1) + " != null)?System.identityHashCode($" + (p + 1) + "):0)");
 			} else {
 				argClasses.add("\"" + c.getName() + "\"");		// ��{�^�̏ꍇ�AgetClass()�ł��Ȃ�����
 				argObjects.add("$" + (p + 1));
diff --git a/TracerOnJavassist/src/tracer/Tracer.java b/TracerOnJavassist/src/tracer/Tracer.java
index 6ac42b5..bbbf256 100644
--- a/TracerOnJavassist/src/tracer/Tracer.java
+++ b/TracerOnJavassist/src/tracer/Tracer.java
@@ -144,7 +144,11 @@
 		for (final CtMethod m : cc.getDeclaredMethods()) {
 			methodInstrumentation(cc, m);
 		}
-		cc.instrument(conv);
+		try {
+			cc.instrument(conv);
+		} catch (CannotCompileException e) {
+			e.printStackTrace();
+		}
 		if (classPath != null) {
 			if (classPath.endsWith("/")) {
 				classPath = classPath.substring(0, classPath.length() - 1);
@@ -165,6 +169,9 @@
 			classInitializer = cc.makeClassInitializer();
 		}
 		classInitializer.insertBefore(outputStatementsGenerator.generateInsertBeforeStatementsForClassDefinition(cc, classInitializer));
+		if (classInitializer.getMethodInfo().getCodeAttribute() != null) {
+			classInitializer.getMethodInfo().getCodeAttribute().computeMaxStack();		// ���ꂪ�Ȃ��ƁA���s����  java.lang.VerifyError: Stack map does not match the one at exception handler... �ŗ�����
+		}
 	}
 
 	private static void methodInstrumentation(final CtClass cc, final CtBehavior m) throws BadBytecode, NotFoundException, CannotCompileException {