Java equals() ordering

Question

If I try to do a .equals() on a null string in java, a null pointer exception will be thrown. I am wondering, if I am trying to compare if a string is equal to

Answer 1

I would keep the "CONSTANT.equals(possibleNull)" code without the null test only if it is a normal condition that the variable could be null - for instance because it just came out of a property map.

Similarly you can get away with not checking for null in instanceof-checks - like:

Food dinner = map.get("dinner");
if (dinner instanceof Soup) {
      ((Soup)blah).eat();
}  // We don't care if it is a Fish or null

But if you really did not expect null, you should explicitly check for that in a separate if-test, and handle it appropriately. It's generally better to catch such data errors early rather than later.