### Question:
IsNull implements Predicate<A> { public boolean test(A obj) { return (null == obj); } IsNull(); boolean test(A obj); @Override boolean equals(Object that); @Override int hashCode(); @Override String toString(); static IsNull<T> instance(); static BinaryPredicate<A, Object> left(); static BinaryPredicate<Object, A> right(); static final IsNull<Object> INSTANCE; static final BinaryPredicate<Object, Object> LEFT; static final BinaryPredicate<Object, Object> RIGHT; }### Answer:
@Test public void testTest() throws Exception { Predicate<Object> p = new IsNull<Object>(); assertTrue(p.test(null)); assertFalse(p.test("foo")); assertFalse(p.test(Integer.valueOf(3))); }