Java_enum枚举

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http://blog.csdn.net/zimo2013/article/details/8928580

1.enum枚举概述

    构造器只能私有private，不允许public修饰，枚举类的方法和数据域可供外部访问。枚举enum只有一个值时，就成了单例。

2.enum常用方法

    1).ordinal()
        返回枚举值在枚举类种的顺序。
        WeekDay2.MON.ordinal();  //返回结果：1
        WeekDay2.WEND.ordinal();  //返回结果：3
    2).compareTo()
        继承了Comparable接口，因此可以比较象与指定对象的顺序，返回的是两个枚举值序号之差.前提：两个枚举值必须属于同一个枚举类，否则会抛出ClassCastException()异常。
        System.out.println(week1.compareTo(week2));//-2
    3).values()
        静态方法，返回一个包含全部枚举值的数组,是数组对象。
    4).name()
        返回枚举常量的名称,与toString()等效
    5).valueOf()
        name()是根据枚举对象获得该对象的名称字符串，而valueOf是根据指定的字符串，来获得对象
    6).equals()
        比较两个枚举类对象的引用。

3.enum枚举内部实现过程

/*
	枚举过程
	Strawberry2013/5/15
*/
public class WeekDay {
	private WeekDay(){}	//为私有 的，即不可new的
	public static final WeekDay SUN = new WeekDay() {//匿名内部类，
		public WeekDay next() {
			return MON;
		}
	};
	public static final WeekDay MON = new WeekDay();
	public static final WeekDay TUES = new WeekDay();
	public static final WeekDay WED = new WeekDay();
	public static final WeekDay TRUR = new WeekDay();
	public static final WeekDay FRI = new WeekDay();
	public static final WeekDay SAT = new WeekDay();
	public abstract WeekDay next();	//抽象的
}

4.使用enum枚举

public enum WeekDay2 {	//可以将enum中的WeekDay2看着一个类名
	SUN {
		public WeekDay next() {
			return MON;
		}
	}, MON,TUES,WEND,;	//举内容为其具体实现对象(注意枚举内容的后面以分号标识)
	private WeekDay2(){}//私有化的构造函数，必须放在枚举的后面
	public abstract WeekDay next();
}

5.enum枚举实例

/*
 	枚举常用实现过程方法
 	Strawberry2013/5/15
 */
public class EnumTest {
	public static void main(String[] args) {
		System.out.println("haha");
		WeekDay1 week1 = WeekDay1.MON;
		WeekDay1 week2 = WeekDay1.WEND;
		System.out.println(week1);
		System.out.println(week1.toString());
		System.out.println(week1.name());//枚举对象的字符串
		System.out.println(week1.ordinal());//顺序号
		System.out.println(WeekDay1.valueOf("MON").ordinal());//返回一个字符串为MON的同名对象
		System.out.println(WeekDay1.values().length);
		System.out.println(week1.compareTo(week2));//返回枚举两个枚举对象的orinal顺序值之差
		//valueOf为枚举静态函数功能，根据
		
		TrafficLamp t = TrafficLamp.RED;
		System.out.println(t.next());
		System.out.println(t.getTime());
	}
	public enum WeekDay1 {
		SUN, MON,TUES,WEND,;
	}
}
enum TrafficLamp {
	RED(30) {	//构造函数以及匿名内部类
		public TrafficLamp next(){
			return GREEN;
		}
	},
	YELLOW(40) {
		public TrafficLamp next(){
			return RED;
		}
	},
	GREEN(5) {
		public TrafficLamp next(){
			return YELLOW;
		}
	};
	public abstract TrafficLamp next();
	private int time;
	private TrafficLamp(int time) {
	this.time = time;
	}
	public int getTime() {
		return time;
	}
}

/*enum的内部实现过程
*/

public class WeekDay {
	private WeekDay(){}
	public static final WeekDay SUN = new WeekDay() {
		public WeekDay next() {
			return MON;
		}
	};
	public static final WeekDay MON = new WeekDay();
	public static final WeekDay TUES = new WeekDay();
	public static final WeekDay WED = new WeekDay();
	public static final WeekDay TRUR = new WeekDay();
	public static final WeekDay FRI = new WeekDay();
	public static final WeekDay SAT = new WeekDay();
	public abstract WeekDay next();
}
//等效于
public enum WeekDay2 {	//可以将enum中的WeekDay2看着一个类名
	SUN, MON,TUES,WEND,;	//举内容为其具体实现对象(注意枚举内容的后面以分号标识)
	private WeekDay2(){}//私有化的构造函数，必须放在枚举的后面
}