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

You should return false if the parameter is null.

To show that this is the standard, see 'Objects.equals(Object, Object) from java.util, that performs an assymetric null check on the first parameter only (on which equals(Object) will be called). From the OpenJDK SE 11 source code (SE 1.7 contains exactly the same):

public static boolean equals(Object a, Object b) {
    return (a == b) || (a != null && a.equals(b));
}

This also handles two null values as equal.