如何检查在 Java 中将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.在实际程序中，a 和 b 在运行时来自别处.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;
}

你如何建议我最好地编码?

How do you suggest I best code this?

更新:a 和 b 在我的场景中总是非负的.

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

推荐答案

Java 8 有 Math.multiplyExact、Math.addExact 等，用于 int 和 long.这些会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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