HashMap concurrent issue

TestHashMap

package org.exoplatform.web.security;

import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;

import junit.framework.TestCase;

import org.exoplatform.services.security.ConversationState;

public class MyTest extends TestCase {
    
    public void testHashMap() throws Exception {
        final ConversationState state = new ConversationState(null);

        final AtomicInteger count = new AtomicInteger(0);
        
        List<Thread> threads = new LinkedList<Thread>();
        final CountDownLatch latch = new CountDownLatch(1);
        for (int i = 0; i < 50; i++) {
            final int idx = i;
            
            Thread t = new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        latch.await();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    
                    for (int j = 0; j < 100; j++) {
                        state.setAttribute("test" + idx + ":" + j, "value" + j);
                    }

                    for (int j = 0; j < 90; j++) {
                        state.removeAttribute("test" + idx + ":" + j);
                    }
                    count.addAndGet(1);
                }
            });
            threads.add(t);
        }
        
        for (Thread t : threads) {
            t.start();
        }
        latch.countDown();
        for (Thread t : threads) {
            t.join();
        }
        
        //
        while (count.get() < 50) {
            Thread.sleep(1000);
        }
        //
        for (int i = 0; i < 50; i++) {
            for (int j = 90; j < 100; j++) {
                assertEquals("value" + i + ":" + j, state.getAttribute("test" + i + ":" + j));                
            }
        }
    }
}