Description Karl Stenerud 2008-08-14 14:28:15 EDT

The following will cause eclipse to issue a "potential null pointer" warning on the last line, even though there's no possibility for s1 to be null at that point.

public boolean areDifferent(String s1, String s2)
{
    if(s1 == null && s2 == null)
    {
        return false;
    }
    if((s1 == null) ^ (s2 == null))
    {
        return true;
    }
    return !s1.equals(s2);
}


As proof, the following lines do not cause a NullPointerException:

areDifferent(null, null);
areDifferent("a", null);
areDifferent(null, "a");
areDifferent("a", "a");