[MATH-1035] Better implementation of checked addition

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.3
• Assignee: Unassigned
• Reporter: derphead
• Created: 17/Sep/13 17:12
• Updated: 19/May/14 15:13
• Resolved: 18/Oct/13 21:41

Description

The implementation of org.apache.commons.math3.util.ArithmeticUtils.addAndCheck(long, long, Localizable) is inefficient and confusing. Here's a better way:

private static long addAndCheck(long a, long b, Localizable pattern) throws MathArithmeticException {
    final long SIGN_BIT = 1L << 63;
    long result = a + b;
    // If a and b have opposite sign, the result will not overflow.
    // If a and b have the same sign, the result overflowed if it has different sign.
    if (((~(a ^ b)) & (a ^ result) & SIGN_BIT) != 0) {
        throw new MathArithmeticException(pattern, a, b);
    }
    return result;
}

This bug tracker is bad btw. It raped my browser.