Positive division, negative result in Java

Question

I'm really puzzled by this. I'm dividing two positive numbers and getting a negative result (I'm using Java).

long hour = 92233720368L / (3600 * 1000000 );

I got as result -132.

But if I divide them as two long numbers, I get the right result:

long hour1 = 92233720368L / (3600000000L );

Then I get as result: 25

I'm wondering why it occurs...

Thank you in advance! :)

Overflow. Your multiplication overflows. Also note that any operation on a `long` or `int` will yield an integral type - the mantissa will be truncated. — Boris the Spider, Jun 17 '14 at 17:23
http://stackoverflow.com/questions/3001836/how-does-java-handle-integer-underflows-and-overflows-and-how-would-you-check-fo — Matt Busche, Jun 17 '14 at 17:23

CMPS · Accepted Answer · 2014-06-17T17:32:12.760

You must add L at the end of 3600 or 1000000:

Example:

long hour = 92233720368L / (3600 * 1000000L );

Here's what's hapenning:

System.out.println(3600 * 1000000); // Gives -694967296 because it exceeds the max limit of an integer size. So 92233720368L / -694967296 = -132

That's exactly what's happening in your division, the dominator is an integer and is considered as negative number for the reason I stated above. So in order to consider the multiplication result of type long you should add L after 3600 or after 1000000

score 2 · Answer 2 · answered Jun 17 '14 at 17:24

2

It interprets 3600 and 10000000 as type int which cannot hold enough information to represent their product, and so you get a different number. You'd have to declare them both as type long to get the correct result.

answered Jun 17 '14 at 17:24

jhobbie

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Positive division, negative result in Java

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