Java，比较BigInteger值 [英] Java, comparing BigInteger values

问题描述

BigInteger bigInteger = ...;


if(bigInteger.longValue() > 0) {  //original code
    //bigger than 0
}

//should I change to this?
if(bigInteger.compareTo(BigInteger.valueOf(0)) == 1) {
    //bigger than 0
}

我需要比较一些任意的BigInteger值。我想知道哪种方法是正确的。鉴于以上代码应该使用哪一个？原始代码在顶部..我正在考虑将其更改为第二种方法。

I need to compare some arbitary BigInteger values. I wonder which approach is correct. Given the above code which one should be used? The original code is on the top.. I am thinking to change it to the second approach.

推荐答案

第一种方法是错误的如果你想测试BigInteger是否有一个正值： longValue 只返回低位64位，这可能会恢复符号...因此，对于积极的BigInteger，测试可能会失败。

The first approach is wrong if you want to test if the BigInteger has a postive value: longValue just returns the low-order 64 bit which may revert the sign... So the test could fail for a positive BigInteger.

第二种方法更好（参见 Bozhos回答进行优化。）

The second approach is better (see Bozhos answer for an optimization).

另一种选择： BigInteger #ignumum 如果值为正，则返回 1 ：

Another alternative: BigInteger#signum returns 1 if the value is positive:

if (bigInteger.signum() == 1) {
 // bigger than 0
}

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