Enum是enumeration(列举)的简写形式,包含在java.lang包中.熟悉C, C++, C#, 或 Pascal人应该对列举有所了解,先看个例子:
public enum Season ...{ winter, spring, summer, fall }
一个enum是定义一组值的对象,它可以包括零个或多个值成员.它是属于enum类型的,一个enum对象中不可有两个或多个相同的属性或值.在次之前的java程序员一般是 用接口的方法实现列举的,如 :
public interface Season ...{
static winter = 0;
static spring = 1; //etc..
}
引入了enum的java的列举的编写方便了许多,只须定义一个enum型的对象.enum对象的值都回自动获得一个数字值,从0开始,依次递增.看一个比较简单的enum实现的例子:EnumDemo.java
/**//*
We can loop over the values we put into the enum
using the values() method.
Note that the enum Seasons is compiled into a
separate unit, called EnumDemo$Seasons.class
*/
public class EnumDemo ...{
/**//*declare the enum and add values to it. note that, like in C#, we don't use a ; to
end this statement and we use commas to separate the values */
private enum Seasons ...{ winter, spring,
summer, fall }
//list the values
public static void main(String[] args) ...{
for (Seasons s : Seasons.values())...{
System.out.println(s);
}
}
}
运行上述代码你回得到 以下结果:
winter
spring
summer
fall
Enum的属性调用:
下面的代码展示了调用enum对象的方法,这也是它通常的用法:
package net.javagarage.enums;
/**//*
File: EnumSwitch.java
Purpose: show how to switch against the values in an enum.
*/
public class EnumSwitch ...{
private enum Color ...{ red, blue, green }
//list the values
public static void main(String[] args) ...{
//refer to the qualified value
doIt(Color.red);
}
/**//*note that you switch against the UNQUALIFIED name. that is, "case Color.red:" is a
compiler error */
private static void doIt(Color c)...{
switch (c) ...{
case red:
System.out.println("value is " + Color.red);
break;
case green:
System.out.println("value is " + Color.green);
break;
case blue:
System.out.println("value is : " + Color.blue);
break;
default :
System.out.println("default");
}
}
}