Eclipse posted this Java puzzle to Twitter today:
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that one should throw a NPE exception at line 10. Almost had me but then I read it again.
b canβt possibly be true. Can it? :-)
I don't know anything about Java. Why not? To the completely untrained eye it sure looks true.
Java has 2 ways of determining if two objects are βthe sameβ. The == operator, and the equals method. Both work differently, and both are shown in the example.
The == operator compares object identity. Creating two String objects and comparing them with == would return false, even if the text is βABCβ both times. Like: two persons can both be called βMartin Fowlerβ, but have distinct identities.
So, my first instinct told me: there are multiple occurrences of βABCβ. So multiple String objects. So the == returns false. Then, Java doesnβt even evaluate the second and operand (after &&). The result of the riddle: false is printed.
Then I looked at the riddle again. Java does heavy optimizing. Strings in Java are immutable, and in the example, βABCβ is not changed. So chances are that there only is exactly 1 βABCβ object.
In that case, the == yields true and the second and operand (with Y) is evaluated. And because Y is null, and calling any method (including equals) on null throws a NullPointerException...
The riddles answer is: nothing is printed. A NullPointerException is thrown.
I guess :-) Am I right?
The answer lies in the Java String pool!
Interesting, thanks for sharing!
NullPointerExceptionforY.equals(null).You can't invoke any method on null reference object :)
Gonna say True. Though not sure if b is True 100% lol
False. :)