java if 语句中 i++ 与 i=i+1 之间有什么区别？
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What's the difference between i++ vs i=i+1 in an if statement?
提问by bwuxiaop
For the 1st code,
对于第一个代码，
int i = 1;
while (i < 10)
if ((i++) % 2 == 0)
System.out.println(i);
The system outputs: 3 5 7 9
系统输出：3 5 7 9
For the 2nd code,
对于第二个代码，
int i = 1;
while (i < 10)
if ((i=i+1) % 2 == 0)
System.out.println(i);
The system outputs: 2 4 6 8 10
系统输出：2 4 6 8 10
Why are the two outputs different but the formula is the same?
为什么两个输出不同但公式相同？
采纳答案by Timo
If you use i++, the old value will be used for the calculation and the value of iwill be increased by 1 afterwards.
如果使用i++，则将使用旧值进行计算，之后 的值i将增加 1。
For i = i + 1, the opposite is the case: It will first be incremented and only then the calculation will take place.
对于i = i + 1，情况正好相反：它将首先递增，然后才会进行计算。
If you want to have the behavior of the second case with the brevity of the first, use ++i: In this case, iwill first be incremented before calculating.
如果您希望第二种情况的行为与第一种情况一样简洁，请使用++i: 在这种情况下，i将在计算之前先递增。
For more details and a more technical explanation, have a look at the docs for Assignment, Arithmetic, and Unary Operators!
有关更多详细信息和更技术性的解释，请查看赋值、算术和一元运算符的文档！
回答by Llogari Casas
i = i+1will increment the value of i, and then return the incremented value.
i = i+1将增加 i 的值，然后返回增加的值。
i++will increment the value of i, but return the original value that i held before being incremented.
i++将递增 i 的值，但返回 i 在递增之前持有的原始值。
