Why int variable value is set to Integer.MAX_VALUE when it was at Integer.MIN_VALUE and decremented

Question

After going through this question, i had one another in my mind. Question: Why an integer variable value is set to Integer.MAX_VALUE.

eg.

int x = Integer.MIN_VALUE;
x--;
if (x == Integer.MAX_VALUE) {
    System.out.println("Why....");
}

There must be some reason that is why this behavior implemented explicitly, otherwise throwing an Exception would be a better idea. I could not find/locate this behavior in JLS.

I assume because creating an exception object and throwing has performance associated with it — Pradeep Simha, Sep 19 '13 at 12:14
@PradeepSimha I don't think performance would be their major concern, as this is rare case, plus functionality can't be compromised over performance. We already have lot of Exceptions in java. — Gaurav Gupta, Sep 19 '13 at 12:24
@Doorknob Not necessarily every other language, but the processor architecture itself. — Kayaman, Sep 19 '13 at 12:32

score 3 · Answer 1 · answered Sep 19 '13 at 12:12

3

Because of underflow. Computers have worked like this for years, throwing an Exception would be a horrible idea here.

answered Sep 19 '13 at 12:12

Kayaman

72,141
5
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But throwing an Exception would be a bad idea, what would be side-effects if `IntegerValueUnderFlowException` would be implemented in place of assigning mathematically as well as logically wrong value. – Gaurav Gupta Sep 19 '13 at 12:17
@GauravGupta The processor works like this too. Granted, it does set flags indicating that underflow occurred, but it's not an error such as dividing by zero. – Kayaman Sep 19 '13 at 12:32

score 2 · Accepted Answer · answered Sep 19 '13 at 13:35

2

http://docs.oracle.com/javase/specs/jls/se7/html/jls-4.html#jls-4.2.2

"The integer operators do not indicate overflow or underflow in any way."

answered Sep 19 '13 at 13:35

tazmanos

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2
9

Why int variable value is set to Integer.MAX_VALUE when it was at Integer.MIN_VALUE and decremented

2 Answers2