java 枚举

枚举类与注解

类的对象是有限个、确定的

当需要定义一组常量时，强烈建议使用枚举类

如果枚举类中只有一个对象，则可作为单例模式的实现方式

如何定义枚举类？

方式一： jdk5.0之前自定义枚举类

package Season;

public class SeasonTest {
	public static void main(String[] args) {
		season spring = season.SPRING;
		season summer = season.SUMMER;
	
	}
}

class season{
	//1.声明season对象的属性:用private、final来修饰
	private final String seasonName;
	private final String seasonDesc;

	// 2.私有化类的构造器,并给属性赋值
	private season(String seasonName,String seasonDesc){
		this.seasonDesc = seasonDesc;
		this.seasonName = seasonName;
	
	}

	// 3.提供当前枚举类的多个对象 声明为public static final
	// static 是为了让其成为类的成员，而不是对象的成员
	public static final season SPRING = new season("春天","春暖花开");
	public static final season SUMMER = new season("夏天","夏日炎炎");
	public static final season AUTUMN = new season("秋天","秋高气爽");
	public static final season WINTER = new season("冬天","冰天雪地");
	// 4.其他诉求1：获取枚举类对象的属性

	public String getSeasonName() {
		return seasonName;
	}
	public String getSeasonDesc() {
		return seasonDesc;
	}
	// 其他诉求2:提供toSring方法
	@Override
	public String toString() {
		return "season [seasonName=" + seasonName + ", seasonDesc=" + seasonDesc + 	"]";
	}
}
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方式二：jdk5.0之后，可以使用enum关键字定义

定义的枚举类默认继承于java.lang.Enum
主要就是定义类的对象的时候不同，并且要先定义

package Season;

public class SeasonTest1 {
	public static void main(String[] args) {
		season1 spring = season1.SPRING;
		System.out.println(spring);
		season1 summer = season1.SUMMER;
	
	}
}

enum season1{
	//1.提供当前枚举类的对象，多个对象之间用，隔开，末尾对象；结束
	SPRING("春天","春暖花开"),
	SUMMER("夏天","夏日炎炎"),
	AUTUMN("秋天","秋高气爽"),
	WINTER("冬天","冰天雪地");


	//1.声明season对象的属性:用private、final来修饰
	private final String seasonName;
	private final String seasonDesc;

	// 2.私有化类的构造器,并给属性赋值
	private season1(String seasonName,String seasonDesc){
		this.seasonDesc = seasonDesc;
		this.seasonName = seasonName;
	
	}


	// 4.其他诉求1：获取枚举类对象的属性

	public String getSeasonName() {
		return seasonName;
	}
	public String getSeasonDesc() {
		return seasonDesc;
	}
	// 其他诉求2:提供toSring方法
	@Override
	public String toString() {
		return "season1 [seasonName=" + seasonName + ", seasonDesc=" + seasonDesc + "]";
	}
}
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Enum中的常用方法

1. toString ,就是打印对象的时候的方法

2. values:看看枚举类中有几个对象

3. valueOf(String Objname) 返回枚举类中对象名是Objname的对象,如果没有Objname的枚举类对象，则抛异常

   public class SeasonTest1 {
   public static void main(String[] args) {
   season1 spring = season1.SPRING;
   System.out.println(spring);
   season1 summer = season1.SUMMER;

    	season1[] values = season1.values();
    	for(int i = 0; i < values.length; i++){
    		System.out.println(values[i]);
    	}
    
    	//valueOf(String Objname) 返回枚举类中对象名是Objname的对象,如果没有Objname的枚举类对象，则抛异常
    	season1 winter = season1.valueOf("WINTER");
    	System.out.println(winter);
    }
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   }

使用enum关键字定义的枚举类实现接口

可以每一个类都实现不同的接口里面的方法。枚举类的对象分别实现接口中的抽象方法

interface info{
	void show();
}
enum season1 implements info{
	//1.提供当前枚举类的对象，多个对象之间用，隔开，末尾对象；结束
	SPRING("春天","春暖花开"){
		public void show(){
			System.out.println("春天");
		}	
	},
	SUMMER("夏天","夏日炎炎"){
		public void show(){
			System.out.println("宁夏");
		}
	},
	AUTUMN("秋天","秋高气爽"){
		public void show(){
			System.out.println("秋天啊秋天");
		}
	},
	WINTER("冬天","冰天雪地"){
		public void show(){
			System.out.println("冬天啊冬天");
		}
	};
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