java number exceeds long.max_value - how to detect?

Posted by jurchiks on Stack Overflow See other posts from Stack Overflow or by jurchiks
Published on 2012-09-10T08:42:54Z Indexed on 2012/09/10 9:38 UTC
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I'm having problems detecting if a sum/multiplication of two numbers exceeds the maximum value of a long integer.
Example code:

long a = 2 * Long.MAX_VALUE;
System.out.println("long.max * smth > long.max... or is it? a=" + a);

This gives me -2, while I would expect it to throw a NumberFormatException...

Is there a simple way of making this work? Because I have some code that does multiplications in nested IF blocks or additions in a loop and I would hate to add more IFs to each IF or inside the loop.

Edit: oh well, it seems that this answer from another question is the most appropriate for what I need: http://stackoverflow.com/a/9057367/540394
I don't want to do boxing/unboxing as it adds unnecassary overhead, and this way is very short, which is a huge plus to me. I'll just write two short functions to do these checks and return the min or max long.

Edit2: here's the function for limiting a long to its min/max value according to the answer I linked to above:

/**
 * @param a : one of the two numbers added/multiplied
 * @param b : the other of the two numbers
 * @param c : the result of the addition/multiplication
 * @return the minimum or maximum value of a long integer if addition/multiplication of a and b is less than Long.MIN_VALUE or more than Long.MAX_VALUE
 */
public static long limitLong(long a, long b, long c)
{
    return (((a > 0) && (b > 0) && (c <= 0))
        ? Long.MAX_VALUE
        : (((a < 0) && (b < 0) && (c >= 0)) ? Long.MIN_VALUE : c));
}

Tell me if you think this is wrong.

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