Java中的char和int [英] char and int in Java

问题描述

我很惊讶地看到这段代码有效。我认为char和int是Java中的两种不同的数据类型，我不得不将char转换为int来为此提供ascii equivelent。为什么这样做？

I was surprised to see this code work. I thought that char and int were two distinct data types in Java and that I would have had to cast the char to an int for this to give the ascii equivelent. Why does this work?

String s = "hello";
int x = s.charAt(1);
System.out.println(x);

推荐答案

A char 可以自动转换为 int 。请参阅 JLS 5.1.2 ：

A char can be automatically converted to an int. See JLS 5.1.2:

以下19种基本类型的特定转换称为扩展基元转换：

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

...

• char to int，long，float或double

...

将有符号整数值扩展为整数类型T只需对符号扩展二进制补码表示整数值填充更宽的格式。 将字符的扩展转换为整数类型T零扩展字符值的表示以填充更宽的格式。

A widening conversion of a signed integer value to an integral type T simply sign-extends the two's-complement representation of the integer value to fill the wider format. A widening conversion of a char to an integral type T zero-extends the representation of the char value to fill the wider format.

（强调补充）

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