Java枚举的应用

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3.可以有若干个公有方法或抽象方法，而采用抽象方法定义的nextDay就将大量的if..else变换成一个一个独立的类

class WeekDay {
	
	private WeekDay(){}
	
	public final static WeekDay SUN = new WeekDay();
	public final static WeekDay MON = new WeekDay();
	public WeekDay nextDay(){
		return (this==SUN)?MON:SUN;
	}
	public String toString(){
		return (this==MON)?"MON":"SUN";
	}
}

public class EnumDemo {

	public static void main(String[] args) {
		System.out.println(WeekDay.SUN.nextDay());
	}
}

也可以是将方法定义为抽象的，每个固定的WeekDay对象的子类去复写的
在一个类中编写完各个枚举类和测试调用类，那么就可以将枚举类定义成调用类的内部类

public abstract class WeekDay {
	
	private WeekDay(){}
	
	public final static WeekDay SUN = new WeekDay(){
		public WeekDay nextDay() {
			return MON;
		};
	};
	public final static WeekDay MON = new WeekDay(){//匿名内部类,子类来写nextDay方法
		public WeekDay nextDay() {
			return SUN;
		};
	};
	public abstract WeekDay nextDay();
	
	public String toString(){
		return (this==MON)?"MON":"SUN";
	}
}

class Demo{}

new Demo(){}  ->new 一个Demo的子类，{}中是子类的代码，这个表示，子类调用的是父类的无参的构造方法
new Demo(20){} ->new子类的实例对象，调用父类的有参的构造方法

枚举的基本应用：

定义一个Week的枚举

枚举是一种特殊的类，其中的每个元素都是该类的一个实例对象，例如可以用WeekDay.SUN.getClass().getName();

public class EnumDemo {
	
	public static void main(String[] args) {
		
		System.out.println(WeekDay.SUN.nextDay());
		Week w = Week.SUN;
		System.out.println(w);
		System.out.println(w.name());
		System.out.println(w.ordinal());//排第几
		System.out.println(w.getClass());
		System.out.println(Week.valueOf("SUN"));//将字符串变换成对应的枚举元素
		System.out.println(Week.values().length);//将枚举中的每一个元素，都装进数组
	}
	
	public enum Week{//定义一个枚举类
		SUN,MON;
	}
}

public enum Week{//定义一个枚举类
		
		SUN,MON;//所有的东西都必须放在枚举值列表下面
		private Week(){System.out.println("WU");};//枚举类的构造方法必须是private
		private Week(int i){System.out.println("I");};
	}

public enum Week{
		
		SUN(5),MON();
		private Week(){System.out.println("WU");};
		private Week(int i){System.out.println("I");};
	}

public class EnumDemo {
	
	public static void main(String[] args) {
		
		System.out.println(Month.March.nextMonth());
		
	}

	public enum Month{
		//January,February,March,April;
		January(31){
			
			public Month nextMonth() {   return February;	}
	
		},February(28) {
			
			public Month nextMonth() {	return March;   }
			
		},March(30) {
			
			public Month nextMonth() {	return April;  }
			
		},April(31) {
			
			public Month nextMonth() {  return January; }
		};
		
		public abstract Month nextMonth();//抽象方法，返回类型是自己类型
		
		private int time ;
		
		private Month(int time){ this.time = time ;}
		
		public String toString(){
			if(this==January)return "January";
			else if(this==February) return "February";
			else if(this==March) return "March";
			else return "April";
		}
	}
}

Java枚举的应用

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原文地址：http://blog.csdn.net/wjw0130/article/details/41960917