Java学习笔记——自动装箱、拆箱 & String初始化

【摘自】http://docs.oracle.com/javase/tutorial/java/data/autoboxing.html

Autoboxing is the
automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes. For example, converting an int to
anInteger, a double to a Double, and so on. If the conversion goes the other
way, this is called unboxing.

自动装箱时一种java编译器的自动转换，把基础数据类型转换为对应的基础数据类型包转类型。

Autoboxing and unboxing lets developers write cleaner code, making it easier to read. The following table lists the primitive types and their corresponding wrapper classes, which are used
by the Java compiler for autoboxing and unboxing:

Primitive type	Wrapper class
boolean	Boolean
byte	Byte
char	Character
float	Float
int	Integer
long	Long
short	Short
double	Double

The Java™ Tutorials上只是提到了基础数据类型自动装箱成为对应的基础数据类型包装类型，最后还强调了对应关系。
对于String，初始化时，这样描述：

Creating Strings

The most direct way to create a string is to write:

String greeting = "Hello world!";

In this case, "Hello world!" is a string literal—a series of characters in your
code that is enclosed in double quotes. Whenever it encounters a string literal in your code,
the compiler
creates
a

String

object with its value—in this case,

Hello
world!

.

这种直接初始化的方式，编译器帮忙把这个字符串常量创建为对应的对象，这里并没有提到自动装箱，只是和自动装箱表面上很类似。