Java中所有的枚举类型都是java.lang.Enum的子类。

1. 定义枚举类型

    简单定义一个枚举类型，如下：

public enum Week {
	MONDAY, 
	TUESDAY, 
	WEDNESDAY, 
	THURSDAY, 
	FRIDAY, 
	SATURDAY, 
	SUNDAY;
}

2. 枚举类型的常用方法

    可以使用枚举类型的values()静态方法返回枚举类型中的所有枚举值，使用枚举常量的name()方法返回枚举常量的名称，使用枚举常量的ordinal()方法返回枚举常量的序数（常量在枚举声明中的位置，从0开始）。示例代码如下：

public static void main(String[] args) {
	//获取枚举类型中的全部枚举值
	Week[] days = Week.values();
	for(Week day : days) {
		//返回枚举常量的名称
		String name = day.name();
		//返回枚举常量的序数（常量在枚举声明中的位置，从0开始）
		int ordinal = day.ordinal();
		String toString = day.toString();
		Class declaringClass = day.getDeclaringClass();
		Class superClass = declaringClass.getSuperclass();
		System.out.println(
				"Name: " + name
				+ "\n" 
				+ "Ordinal: " + ordinal
				+ "\n" 
				+ "ToString: " + toString
				+ "\n" 
				+ "DeclaringClass: " + declaringClass
				+ "\n" 
				+ "SuperClass: " + superClass
				+ "\n" 
			);
	}
}

Name: MONDAY
Ordinal: 0
ToString: MONDAY
DeclaringClass: class myEnum.Week
SuperClass: class java.lang.Enum

Name: TUESDAY
Ordinal: 1
ToString: TUESDAY
DeclaringClass: class myEnum.Week
SuperClass: class java.lang.Enum

Name: WEDNESDAY
Ordinal: 2
ToString: WEDNESDAY
DeclaringClass: class myEnum.Week
SuperClass: class java.lang.Enum

Name: THURSDAY
Ordinal: 3
ToString: THURSDAY
DeclaringClass: class myEnum.Week
SuperClass: class java.lang.Enum

Name: FRIDAY
Ordinal: 4
ToString: FRIDAY
DeclaringClass: class myEnum.Week
SuperClass: class java.lang.Enum

Name: SATURDAY
Ordinal: 5
ToString: SATURDAY
DeclaringClass: class myEnum.Week
SuperClass: class java.lang.Enum

Name: SUNDAY
Ordinal: 6
ToString: SUNDAY
DeclaringClass: class myEnum.Week
SuperClass: class java.lang.Enum

3. 比较枚举常量

    判断两个枚举类型常量的值是否相等，可以直接使用“==”，而不用equals()方法。比较两个枚举类型常量的值的大小，可以使用compareTo()方法。

public static void main(String[] args) {
	Week mon = Week.MONDAY;
	Week tues = Week.TUESDAY;
	Week wed = Week.WEDNESDAY;
	//比较枚举常量，实际上是比较它们序数的大小
	System.out.println(mon.compareTo(tues));
	System.out.println(tues.compareTo(wed));
	System.out.println(wed.compareTo(mon));
}

输出结果如下：

-1
-1
2

public final int compareTo(E o) {
	Enum other = (Enum)o;
	Enum self = this;
	if (self.getClass() != other.getClass() && // optimization
            self.getDeclaringClass() != other.getDeclaringClass())
	    throw new ClassCastException();
	return self.ordinal - other.ordinal;
}

4. 创建枚举常量

    创建枚举常量主要有三种方法：直接利用枚举类型创建枚举常量、使用Enum的valueOf()静态方法创建枚举常量、使用枚举类型的valueOf()静态方法创建枚举常量。

//直接创建枚举常量
Week mon = Week.MONDAY;
//使用Enum的valueOf()静态方法创建枚举常量
Week tues = Enum.valueOf(Week.class, "TUESDAY");
//使用枚举类型的valueOf()静态方法创建枚举常量
Week wed = Week.valueOf("WEDNESDAY");

5. 定义高级的枚举类型

    根据需要，可以在枚举类型中添加构造器、方法和字段，还可以让枚举类型继承接口。

    定义接口IWeek，如下：

public interface IWeek {
	public void println();
}

public enum AdvancedWeek 
	implements IWeek{
	
	MONDAY("星期一", "Mon."), 
	TUESDAY("星期二", "Tues."), 
	WEDNESDAY("星期三", "Wed."), 
	THURSDAY("星期四", "Thurs."), 
	FRIDAY("星期五", "Fri."), 
	SATURDAY("星期六", "Sat."), 
	SUNDAY("星期日", "Sun.");
	
	private String nameCn;
	private String abbreviation;
	
	//构造方法只能为private
	private AdvancedWeek() {}

	private AdvancedWeek(String nameCn, String abbreviation) {
		this.setNameCn(nameCn);
		this.setAbbreviation(abbreviation);
	}

	public String getNameCn() {
		return nameCn;
	}

	public void setNameCn(String nameCn) {
		this.nameCn = nameCn;
	}

	public String getAbbreviation() {
		return abbreviation;
	}

	public void setAbbreviation(String abbreviation) {
		this.abbreviation = abbreviation;
	}
	
	public void println() {
		System.out.println(this.ordinal() + " - " + this.name() + " - " + this.getAbbreviation() + " - " + this.getNameCn());
	}
}

    测试AdvancedWeek，如下：

public static void main(String[] args) {
	AdvancedWeek[] days = AdvancedWeek.values();
	for(AdvancedWeek day : days) {
		day.println();
	}
}

0 - MONDAY - Mon. - 星期一
1 - TUESDAY - Tues. - 星期二
2 - WEDNESDAY - Wed. - 星期三
3 - THURSDAY - Thurs. - 星期四
4 - FRIDAY - Fri. - 星期五
5 - SATURDAY - Sat. - 星期六
6 - SUNDAY - Sun. - 星期日

Java中的枚举类型Enum

原文：http://blog.csdn.net/snarlfuture/article/details/18996037