Post和Pre增量运算符 [英] Post and Pre increment operators

问题描述

当我运行以下示例时，我得到输出0,2,1

When i run the following example i get the output 0,2,1

class ZiggyTest2{

        static int f1(int i) {  
            System.out.print(i + ",");  
            return 0;  
        } 

        public static void main(String[] args) {  
            int i = 0;  
            int j = 0;  
            j = i++;   //After this statement j=0 i=1
            j = j + f1(j);  //After this statement j=0 i=1
            i = i++ + f1(i);  //i++ means i is now 2. The call f1(2) prints 2 but returns 0 so i=2 and j=0
            System.out.println(i);  //prints 2?
        } 
    } 

我不明白为什么输出为0， 2,1而不是0,2,2

I don't understand why the output is 0,2,1 and not 0,2,2

推荐答案

 i = i++ + f1(i);  

i ++ 表示我现在 2 。调用 f1（i）打印 2 但返回0，所以 i = 2 和 j = 0

i++ means i is now 2. The call f1(i) prints 2 but returns 0 so i=2 and j=0

在此 i = 1 ，现在想象 f1（）调用并替换为0

before this i = 1 , now imagine f1() called and replaced with 0

所以

i = i++ + 0;

现在它将是

i = 1 + 0 // then it will increment i to 2 and then (1 +0) would be assigned back to `i`

---

简单来说（来自这里 @ Piotr）

i = i ++粗略转换为

"i = i++" roughly translates to

int oldValue = i; 
i = i + 1;
i = oldValue; 

---

另一个这样的例子：

---

Another such Example :

• 这里的基本工作相同

• The same fundamental works here

这篇关于Post和Pre增量运算符的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！