IdentityCheck

From APIDesign

Is there an externally observable difference between following programs?

public static String sayHello() {
  return "Hello World!";
}

public static void sayHello() {
  return "Hello" + " World!";
}

Of course, there is! Just call the method twice:

assert sayHello() == sayHello();

The first version of the method passes the IdentityCheck test. The second does not. There are also other differences in MemoryAllocations as well as StringsUsedInConstantPool.