如题,
我自己测试的时候,如果两个int型大数相乘,结果为负,求检测溢出的方法,并掷出异常的代码
2条回答 默认 最新
- _1_1_7_ 2011-10-20 19:01关注
[code="java"]
/**
* Multiply two integers, checking for overflow.
*
* @param x a factor
* @param y a factor
* @return the productx*y
* @throws ArithmeticException if the result can not be represented as an
* int
* @since 1.1
*/
public static int mulAndCheck(int x, int y) {
long m = ((long)x) * ((long)y);
if (m < Integer.MIN_VALUE || m > Integer.MAX_VALUE) {
throw new ArithmeticException("overflow: mul");
}
return (int)m;
}/** * Multiply two long integers, checking for overflow. * * @param a first value * @param b second value * @return the product <code>a * b</code> * @throws ArithmeticException if the result can not be represented as an * long * @since 1.2 */ public static long mulAndCheck(long a, long b) { long ret; String msg = "overflow: multiply"; if (a > b) { // use symmetry to reduce boundary cases ret = mulAndCheck(b, a); } else { if (a < 0) { if (b < 0) { // check for positive overflow with negative a, negative b if (a >= Long.MAX_VALUE / b) { ret = a * b; } else { throw new ArithmeticException(msg); } } else if (b > 0) { // check for negative overflow with negative a, positive b if (Long.MIN_VALUE / b <= a) { ret = a * b; } else { throw new ArithmeticException(msg); } } else { // assert b == 0 ret = 0; } } else if (a > 0) { // assert a > 0 // assert b > 0 // check for positive overflow with positive a, positive b if (a <= Long.MAX_VALUE / b) { ret = a * b; } else { throw new ArithmeticException(msg); } } else { // assert a == 0 ret = 0; } } return ret; }
[/code]
以上是commons-math-2.2的源码
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