PriorityQueue queue =  new PriorityQueue(10, comparator);

            BuildCompleted e1 = new BuildCompleted();
            e1._time = new Timestamp(1377950159);

            Battle b1 = new Battle();
            b1._time = new Timestamp(1377950150);

            queue.add(e1);
            queue.add(b1);

            while (true) {
                ??? e = (BuildCompleted)queue.poll();
                if(e == null) {
                    break;
                }
                System.out.println(e.getTimeStamp());
            }

if(a instanceof Class1) {
   Class1 x = ...
} else if (a instanceof Class2) {
   Class2 x = ...
}

x.run(); 

public abstract class Test {

    public abstract void run();

}

public class TestExt extends Test {


    protected int localMethod()
    {
        return 1;
    }

    public void run()
    {
        System.out.println(this.localMethod());
    }
}

        Test test = new TestExt();
        test.run();