test/jdk/java/util/HashMap/HashMapCloneLeak.java

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/**
 * @test
 * @bug 7042126
 * @summary Verify that we do not leak contents when we clone a HashMap
 * @author david.buck@oracle.com
 * @run main/othervm HashMapCloneLeak
 * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:+EliminateAutoBox -XX:AutoBoxCacheMax=20000 HashMapCloneLeak
 */

import java.util.HashMap;
import java.lang.ref.WeakReference;

public class HashMapCloneLeak {

    static WeakReference<Object> wr = null;

    // helper method to keep testObject and map out of main method's scope
    private static HashMap<Integer, Object> makeMap() {
        HashMap<Integer, Object> map = new HashMap<Integer, Object>();
        Object testObject = new Object();
        wr = new WeakReference<Object>(testObject);
        map.put(42, testObject);
        return map;
    }

    public static void main(String[] args) throws Exception {
        HashMap<Integer, Object> hm = makeMap();
        hm = (HashMap<Integer, Object>)hm.clone();
        hm.clear();
        // There should no longer be a strong reference to testObject
        // the WeakReference should be nulled out by GC. If not,
        // we will hang here until timed out by the test harness.
        Object[] chain = null;
        while (wr.get() != null) {
            try {
                Object[] allocate = new Object[1000000];
                allocate[0] = chain;
                chain = allocate;
            } catch (OutOfMemoryError oome) {
                chain = null;
            }
            System.gc();
            Thread.sleep(100);
        }
    }

}