### Question:
IsNull implements Predicate<A> { public static <T> IsNull<T> instance() { return new IsNull<T>(); } 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 testConstant() throws Exception { assertEquals(IsNull.instance(), IsNull.instance()); }