Need reviewer: JDK 8 CR for Support Integer overflow (original) (raw)

Eamonn McManus eamonn at mcmanus.net
Fri Feb 3 17:52:36 UTC 2012

My initial remarks:

In negateExact, the condition x == -x should be faster to evaluate than x == Integer.MIN_VALUE and reflects the intent just as well.

In addExact and subtractExact, I would be inclined to implement the int versions using long arithmetic, like this:

long lr = x + y; int r = (int) lr; if (r == lr) { return r; } else { throw... }

I would use this technique of cast-and-compare in the int multiplyExact instead of comparing against MIN_VALUE and MAX_VALUE, and especially in toIntExact(long).

I agree with Stephen Colebourne that brief implementation comments would be useful. But I disagree with his proposed further methods in Math (increment, decrement, int+long variants), which I don't think would pull their weight.

Éamonn

On 2 February 2012 12:15, Roger Riggs <Roger.Riggs at oracle.com> wrote:

There is a need for arithmetic operations that throw exceptions when the results overflow the representation of int or long.

The CR is 6708398: Support integer overflow <http://bugs.sun.com/**_ _bugdatabase/viewbug.do?bug**id=6708398<http://bugs.sun.com/bugdatabase/viewbug.do?bugid=6708398> > Please review this webrev <http://cr.openjdk.java.net/%**_ _7Erriggs/CR6708398/webrev/<http://cr.openjdk.java.net/%7Erriggs/CR6708398/webrev/>> to add static methods in java.lang.Math to support addExact(), subtractExact(), negateExact(), multiplyExact(), and toIntExact() for int and long primitive types. Thanks, Roger Riggs

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