Asserting Nullness

• public static void assertNull(Object o)

• public static void assertNull(String message, Object o)

e.g. testing for memory leak:

    public void testMemoryLeak() throws InterruptedException {
        Complex z1 = new Complex(-2, 0);
        WeakReference ref = new WeakReference(z1);
        z1 = null;
        System.gc();
        System.gc();
        System.gc();
        Thread.sleep(1000);
        assertNull(ref.get());
    }