Java ++运算符

Question

所以我正在测试运营商,因为我用java帮助我的朋友,我偶然发现了一个奇怪的编程顺序.运行以下代码时发生了什么

public static void main(String[] args) {
    int B = 6;
    //First console print out
    System.out.println(B+=++B);
    System.out.println(B);
    B = 6;
    //Second Console print out
    System.out.println(B+=B++);
    System.out.println(B);
}

以下代码的输出是

13
13

12   
12

是什么原因导致第二个控制台B数学输出= 12时它自己加6,然后是++(这是+1)

Answer 1

这里的区别在于增量运算符.

在这种情况下B += ++B,B增加到7并加到它的旧自己(6)以达到13.

在这种情况下B += B++,B被添加到自身,给出12,然后执行++并将结果存储在B中,但计算结果然后存储在B中的++上.因此给出12作为输出.

Answer 2

ACTION       EFFECT   NOTES
----------   ------   -----
B = 6        B = 6
B += (++B)   B += 7   // B is incremented and the value is returned
B            B = 13

B = 6        B = 6
B += (B++)   B += 6   // The current value of B is the result of (B++) and B is
                      // incremented *after* the (B++) expression; however, the
                      // assignment to B (+=) happens after the (++) but it does
                      // not re-read B and thereby covers up the post increment.
B            B = 12