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From Jim Yu <junjie0...@gmail.com>
Subject [classlib][luni] HashMap doesn't support proxy object as keys
Date Thu, 18 Jun 2009 06:52:44 GMT
Hi all,

There is an interesting edge case in HashMap. If we use a proxy object as
the key to put something into HashMap, we will fail to retrieve the value by
using that key. But RI works well for this case. Here is a test case below
to present the problem. I found the root cause of the failure for our
HashMap is that proxyInstance.equals(proxyInstance) returns false which
sounds strange but appears work correctly as both Harmony and RI behave so.
I suspect RI has made some special approaches to match the key when the key
is a proxy object. So I would be inclined to follow RI's behavior in this
case. Any thoughts here?

I have raised a JIRA at
https://issues.apache.org/jira/browse/HARMONY-6237for this issue.

public interface MockInterface {
    public String mockMethod();

public class MockClass implements MockInterface {
    public String mockMethod() {
        return "This is a mock class.";

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.HashMap;
import java.util.Map;

public class TestProxy implements InvocationHandler {

    Object obj;

    public TestProxy(Object o) {
        obj = o;

    public Object invoke(Object proxy, Method m, Object[] args)
            throws Throwable {

        Object result = null;

        try {

            result = m.invoke(obj, args);

        } catch (Exception e) {
        } finally {
        return result;

    public static void main(String[] argv) throws Exception {

        MockInterface proxyInstance = (MockInterface)
                new Class[] { MockInterface.class }, new TestProxy(
                        new MockClass()));

        Map hm = new HashMap();

        hm.put(proxyInstance, "Value");

        Object o = hm.get(proxyInstance);

        System.out.println("Value got for proxy object key:" + o);



Value got for proxy object key:null

Value got for proxy object key:Value

Best Regards,
Jim, Jun Jie Yu

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