Is it a bad idea if equals(null) throws NullPointerException instead?

Question

The contract of equals with regards to null, is as follows:

For any non-null reference value x, x.equals(null) sho

Answer 1

Not that this is neccessarily an answer to your question, it is just an example of when I find it useful that the behaviour is how it is now.

private static final String CONSTANT_STRING = "Some value";
String text = getText();  // Whatever getText() might be, possibly returning null.

As it stands I can do.

if (CONSTANT_STRING.equals(text)) {
    // do something.
}

And I have no chance of getting a NullPointerException. If it were changed as you suggested, I would be back to having to do:

if (text != null && text.equals(CONSTANT_STRING)) {
    // do something.
}

Is this a good enough reason for the behaviour to be as it is?? I don't know, but it is a useful side-effect.