Signal { public static void raise(Signal signal) throws IllegalArgumentException { Objects.requireNonNull(signal); sun.misc.Signal.raise(unwrap(signal)); } Signal(String name); int getNumber(); String getName(); @Override boolean equals(Object other); @Override int hashCode(); @Override String toString(); static synchronized SignalHandler handle(final Signal signal,
      final SignalHandler signalHandler); static void raise(Signal signal);  }
@Test public void raiseNullThrowsException() { assertThatThrownBy(() -> Signal.raise(null)).isInstanceOf(NullPointerException.class); }