Java null String equals result

Question

Please help me how does the string.equals in java work with null value? Is there some problem with exceptions? Three cases:

boolean result1,result2, result3;         


        

Answer 1

That piece of code will throw a NullPointerException whenever string1 is null and you invoke equals on it, as is the case when a method is implicitly invoked on any null object.

To check if a string is null, use == rather than equals.

Although result1 and result3 will not be set due to NullPointerExceptions, result2 would be false (if you ran it outside the context of the other results).