if语句中i ++与i = i + 1的区别是什么？ [英] What's the difference between i++ vs i=i+1 in an if statement?

问题描述

对于第一个代码，

int i = 1;
while (i < 10)
    if ((i++) % 2 == 0)
        System.out.println(i);

系统输出：3 5 7 9

The system outputs: 3 5 7 9

对于第二个代码，

int i = 1;
while (i < 10)
    if ((i=i+1) % 2 == 0)
        System.out.println(i);

系统输出：2 4 6 8 10

The system outputs: 2 4 6 8 10

为什么两个输出不同但公式相同？

Why are the two outputs different but the formula is the same?

推荐答案

如果您使用 i ++ ，旧值将用于计算，之后 i 的值将增加1。

If you use i++, the old value will be used for the calculation and the value of i will be increased by 1 afterwards.

对于 i = i + 1 ，情况恰恰相反：它将首先递增，然后才会进行计算。

For i = i + 1, the opposite is the case: It will first be incremented and only then the calculation will take place.

如果您希望第二种情况的行为与第一种情况相同，请使用 ++ i ：In在这种情况下， i 将在计算之前首先递增。

If you want to have the behavior of the second case with the brevity of the first, use ++i: In this case, i will first be incremented before calculating.

有关详细信息和更多技术说明，请使用查看分配，算术和一元运算符的文档！

For more details and a more technical explanation, have a look at the docs for Assignment, Arithmetic, and Unary Operators!

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