三元运算符返回意外输出[重复]

Question

此问题已经在这里有了答案：

What is the type of a ternary expression with int and char operands? [duplicate] （1个答案）

[<18天前关闭。

已经问过这个主题，但我听不懂。您将在下面找到我的程序。当我运行该程序时，它显示X和88。删除int i = 0的声明时，它返回X和X。我在这里找到了一些解释：Unexpected output when using a ternary operator and final variable，但我不太明白。我不明白为什么该程序返回X和88而不是X和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);
    }
}

Answer 1

请在此处阅读ternary operator的规则

https://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.25

第一个是If one of the operands is of type T where T is byte, short, or char, and the other operand is a constant expression of type int whose value is representable in type T, then the type of the conditional expression is T.的结果

在这种情况下，T为字符类型，并且常量表达式为0

所以输出是char类型，它是

x

---

第二个是Otherwise, binary numeric promotion is applied to the operand types, and the type of the conditional expression is the promoted type of the second and third operands.的情况

在此处https://docs.oracle.com/javase/specs/jls/se7/html/jls-5.html#jls-5.6.2了解有关二进制数值的促销信息>>

第2点的最后一种情况在这里适用

Otherwise, both operands are converted to type int.并将char转换为int给出其ascii值，该值为88因此输出为88