Strange Calculation Behavior in Java

Question

Why is the Result of first calculation bigger than the second calculation?

System.out.println(new Date().getTime() - (1000*60*60*24*30*3));
System.out.println(new Date().getTime() + (1000*60*60*24*30*3));

Result:

Info:   1440788283924
Info:   1439160414740

because the value of `1000*60*60*24*30*3` is `-813934592` – SomeJavaGuy Aug 19 '15 at 08:57 — SomeJavaGuy, Aug 19 '15 at 08:57
May be executing time defference – Rafiq Aug 19 '15 at 09:00 — Rafiq, Aug 19 '15 at 09:00
@Rafiq No. It's because of overflow. – Suresh Atta Aug 19 '15 at 09:07 — Suresh Atta, Aug 19 '15 at 09:07

score 2 · Answer 1 · answered Aug 19 '15 at 09:00

2

The expression

1000*60*60*24*30*3

results in 32-bit integer overflow. One way to fix it is by making the first operand a long, which will force the entire expression into the long type:

1000L*60*60*24*30*3

answered Aug 19 '15 at 09:00

Marko Topolnik

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score 1 · Answer 2 · answered Aug 19 '15 at 08:58

1

Integeroverflow is happening in your case and the value of 1000*60*60*24*30*3 becoming -813934592

answered Aug 19 '15 at 08:58

Suresh Atta

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Ah okay i understand. Thanks :) – GermanGuy Aug 19 '15 at 09:02
@ANDREvolution You are welcome :) – Suresh Atta Aug 19 '15 at 09:06

Strange Calculation Behavior in Java

2 Answers2