Java char 也是 int 吗？

Question

我试图为类完成一些代码:

public int getValue(char value) {
    if (value == 'y') return this.y;
    else if (value == 'x') return this.x;

由于我可能最终无法返回任何东西，它告诉我最后这样做:

return value;

这让我感到惊讶，因为该方法的返回类型是 int 类型。然而，它告诉我返回一个 char!我正在使用 Eclipse，并且习惯了无穷无尽的警告和其他东西，这是一个很大的惊喜。

那么，char 真的是 int 吗？为什么会这样？

Answer 1

Java Language Specification州

When a return statement with an Expression appears in a method declaration, the Expression must be assignable (§5.2) to the declared return type of the method, or a compile-time error occurs.

管理一个值是否可分配给另一个值的规则定义为

Assignment contexts allow the use of one of the following:

• a widening primitive conversion (§5.1.2)

和

19 specific conversions on primitive types are called the widening primitive conversions:

• char to int, long, float, or `double

最后

A widening primitive conversion does not lose information about the overall magnitude of a numeric value in the following cases, where the numeric value is preserved exactly: [...]

A widening conversion of a char to an integral type T zero-extends the representation of the char value to fill the wider format.

简而言之，作为return 语句表达式的char 值可以通过扩展原始类型转换分配给int 的返回类型。