Post 和预增量运算符 OCJA-1.8

Question

我正在练习 java post 和预递增运算符，我对理解下面程序的输出感到困惑。它如何将输出生成为“8”？

public class Test{

public static void main(String [] args){
    int x=0;
    x=++x + x++ + x++ + ++x;
    System.out.println(x);
   }    
}

我尝试了更多示例程序，我可以在其中跟踪输出

public class Test{
 public static void main(String [] args){
    int x=0;
    x=++x + ++x + ++x + x++;
    //  1 + 2 + 3 + 3 =>9
    System.out.println(x);
  } 
}

Answer 1

这可以说与以下内容相同：

public static void main(String[] args) {
    int x=0;
    int t1 = ++x;
    System.out.println(t1);//t1 = 1 and x = 1
    int t2 = x++;
    System.out.println(t2);//t2 = 1 and x = 2
    int t3 = x++;
    System.out.println(t3);//t3 = 2 and x = 3
    int t4 = ++x;
    System.out.println(t4);//t4 = 4 and x = 4

    x= t1 + t2 + t3 + t4;//x = 1 + 1 + 2 + 4
    System.out.println(x);//8
}

Answer 2

这可能有助于理解预运算符和 post 运算符的行为。

 public class Test{

    public static void main(String [] args){
        int x=0;
        x =   ++x   +  x++   +      x++  +     ++ x;
      //0 = (+1+0)  + (1)    + (+1 +1)   + (+1 +1 +2);
      //0  = 1      + 1      +  2      +  4
         System.out.println(x); // prints 8.
       }    
    }

Post 和预增量运算符 OCJA-1.8

Post and Pre Increment Operator OCJA-1.8

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operators

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pre-increment

post-increment