Bad cache

gistfile1.java

import java.util.ArrayList;
import java.util.UUID;
import java.util.WeakHashMap;

import org.junit.Test;


public class BadCache {
	@Test
	public void test() {
		final WeakHashMap<String, CacheObject> cache = new WeakHashMap<String, CacheObject>();
		final ArrayList<String> keyList = new ArrayList<String>();

		new Thread(new Runnable() {
			public void run() {
				for(;;) {
					int i=0;
					synchronized (cache) {
						long from = System.currentTimeMillis();
						for(String key: cache.keySet()) {
							CacheObject obj = cache.get(key);
							if (obj.expires < from) {
								i++;
								keyList.remove(key);
							}
						}
						System.out.println("Removed Cache="+ i + ", " + (System.currentTimeMillis() - from) + "ms");
					}
					try {
						Thread.sleep(1000);
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}
			}
		}).start();

		for (;;) {
			String key = UUID.randomUUID().toString();
			synchronized(cache) {
				CacheObject obj = new CacheObject();
				obj.expires = Math.round(Math.random() * 10000);
				obj.obj = UUID.randomUUID().toString();
				cache.put(key, obj);
				if (keyList.size() < 10000)
					keyList.add(key);
			}
		}
	}

	static class CacheObject {
		public long expires;
		public String obj;
	}
}