A similar but arguably more useful version of this is when you have two variables, one of which may be null. Traditionally you issue an if-condition test using the variable user input as the left operand but switching it handles the null case automatically.

Ex:

    Foo SOME_CONSTANT = <something-not-null>;

    Foo userSuppliedInput = <some-user-input-possibly-null>;

    // This can raise an null pointer exception
    if (userSuppliedInput.isEquals(SOME_CONSTANT) {
        // ...
    }

    // This can't raise a null pointer exception (assuming isEquals handles nulls properly):
    if (SOME_CONSTANT.isEquals(userSuppliedInput) {
        // ...
    }