Overflow Handling in Java

[madhes]

Hi,
Is there any direct way to find, whether overflow occured in a computation, in Java. For eg., assume the following code segment:

byte a = 10, b = 120, c = a + b;

here, overflow occured and 'c' wil have a wrong value, instead of 130, (since a byte can hold only upto +128). I just want to know is there any specific way to check whether overflow occured or not.
thanks,
madhes

 

[toolkit]

Actually, the code:

byte a  = 10;
byte b  = 120;
byte c = a + b;

Does not compile with my version of javac, instead it complains:
[tt]
Overflow.java:line-no: possible loss of precision
found: int
required: byte
byte c = a + b;
^
1 error
[/tt]
What you should do therefore is:

try {
    int c = a + b;
    if( (byte)c != c ) {
        throw new Exception( "byte overflow occured" );
    }
} catch( Exception e ) {
    e.printStackTrace();
}

Anyone with a more elegant answer? Cheers Neil

 

[madhes]

Thanks.
The results are casted to the upper types, for only byte and short. If the operands are of integer types, the result will be again an integer, & compiler will not throw any error. Since we use int and long in our applications widely, i need a mechanism to detect the overflow.
Consider the following example,

int a = Integer.MAX_VALUE, b = 2; 
long c = a + b; (or) int c = a + b;

The above expression, gives the result as -2147483647, which is wrong. When we cast the result into long, then we get the correct result.
i.e.,

long c = (long) a + b; // CORRECT, now c = 2147483649.

OK.
Now i come to my problem. Since, java doesnt have any mechanism to handle the overflow, i wrote the code like, for adding two integers,

boolean isOverFlow(int a, int b) {
    long result = (long) a + b;
    if (result < Integer.MIN_VALUE || result > Integer.MAX_VALUE) {
        return true;
    }
    return false;
}

I just want to know, is there any better mechanism than this.
thanks,
Madhes.