java - SCJP程序给出输出8 2怎么办？

Question

class Foozit {
    public static void main(String[] args) {
        Integer x = 0;
        Integer y = 0;
        for (Short z = 0; z < 5; z++) {
            if ((++x > 2) || ++y > 2)
                x++;
        }
        System.out.println(x + "Hello World!" + y);
    }
}

我尝试了这段 scjp 代码，得到的输出是 5 3 谁能告诉我哪里出错了

Answer 1

循环执行5次(z从0到4)

在 if 条件下，++x 被计算了五次。但是只有当条件的第一部分为假时，++y 才会被评估。

即，这种情况:

if ((++x > 2) || ++y > 2)

变成:

//1st iteration 
if( 1 > 2 || 1 > 2 ) //False, x++ is not evaluated

//2nd iteration
if( 2 > 2 || 2 > 2 ) //False, x++ is not evaluated

//3rd iteration 
if( 3 > 2 || 2 > 2 ) //True, the second ++y is skipped, but x++ is evaluated, x becomes 4

//4th iteration 
if( 5 > 2 || 2 > 2 ) //True, the second ++y is skipped, but x++ is evaluated, x becomes 6

//5th iteration
if( 7 > 2 || 2 > 2 ) //True, the second ++y is skipped, but x++ is evaluated, x becomes 8

最后，我们有:

x = 8 and y = 2

记住:++x 是预递增(想想改变和使用)而 x++ 是后递增(想想使用和改变)