public class ReverseNullExample { public static Object callA(Object o) { return "hi"; } public static Object callB(Object o) { return o.toString(); } public static String testA(Object o) { // callB dereferences o, making the later check a bug // if this were callA, no bug would be reported here. System.out.println(callB(o)); if( o == null ) { System.out.println("It's null"); } return "done"; } }