三元运算符返回意外的输出

由 kautem发布于 2020-05-24 07:02:25 Javaternary

This subject is already asked but I didn't understand it. You'll find my program below. When I run this program it prints X and 88. When I remove do the declaration of int i = 0 it returns X and X. I found some explanations here : Unexpected output when using a ternary operator and final variable but i didn't understand it so much. I don't understand why this program returns X and 88 instead of X and X.

public class Ternary {
    public static void main(String[] args) {
        char x = 'X';
        int i = 0;
        System.out.println(true  ? x : 0);
        System.out.println(false ? i : x);
    }
}

ut_quo 2020-05-24 07:02:25 回复

该声明

System.out.println(true  ? x : 0);

可以写成

if(true) {
    System.out.println(x);
} else {
    System.out.println(0);
}

which will print X

同样，声明

System.out.println(false ? i : x);

可以写成

if(false) {
    System.out.println(i);
} else {
    System.out.println(x);
}

which will print X

Thus, the output is X and X.

蛋小疼 2020-05-24 07:02:25 回复
Both paths through the ternary must be of the same type. char can (and is) widened to an int yielding the ascii value 88 instead of X.
```
System.out.println(false ? (char) i : x);
```
而且两者都将输出
```
X
X
```