如何检查Java中的两个数字相乘是否会导致溢出？ [英] How can I check if multiplying two numbers in Java will cause an overflow?

问题描述

我想处理两个数字相乘导致溢出的特殊情况。代码如下所示：

I want to handle the special case where multiplying two numbers together causes an overflow. The code looks something like this:

int a = 20;
long b = 30;

// if a or b are big enough, this result will silently overflow
long c = a * b;

这是一个简化版本。在真实程序中，和 b 在运行时的其他位置获取。我想要实现的是这样的：

That's a simplified version. In the real program a and b are sourced elsewhere at runtime. What I want to achieve is something like this:

long c;
if (a * b will overflow) {
    c = Long.MAX_VALUE;
} else {
    c = a * b;
}

您如何建议我最好的代码？

How do you suggest I best code this?

更新： a 和 b 在我的方案中始终为非负数。

Update: a and b are always non-negative in my scenario.

推荐答案

Java 8有 Math.multiplyExact ，数学对于int和long，.addExact 等。这些在溢出时抛出未经检查的 ArithmeticException 。

Java 8 has Math.multiplyExact, Math.addExact etc. for ints and long. These throw an unchecked ArithmeticException on overflow.

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