枚举类（自定义实现枚举类）

枚举概述：

是指将变量的值一一列出来，变量的值只限于列举出来的值的范围内。举例：一周只有7天，一年只有12个月等

回想单例设计模式：单例类是一个类只有一个实例

那么多例类就是一个类有多个实例，但不是无限个数的实例，而是有限个数的实例，这才能是枚举类

自己实现枚举：

自定义枚举类

案例1：无参构造

案例2：带参构造，get方法，toString方法

案例3：抽象方法

发现自己定义一个枚举类，比较麻烦，所有java就提供了枚举类供我们使用

格式是：只有枚举项的枚举了

public enum 枚举类名{

枚举项1，枚举项2，枚举项3...；

}

自定义枚举类代码实现：

package com.aynu3;public class Light {//创建三个实例public static final Light RED = new Light();public static final Light GREEN = new Light();public static final Light YELLOW = new Light();private Light(){}
}

package com.aynu3;public class Light2 {//创建三个实例public static final Light2 RED = new Light2("红");public static final Light2 GREEN = new Light2("绿");public static final Light2 YELLOW = new Light2("黄");private String name;private Light2(String name){this.name=name;}public String getName(){return name;}public String toString(){return "Light2{"+"name='"+name +'\''+'}';}
}

package com.aynu3;public abstract class Light3 {//创建三个实例public static final Light3 RED = new Light3("红"){@Overridepublic void show() {System.out.println("红");}};public static final Light3 GREEN = new Light3("绿"){@Overridepublic void show() {System.out.println("绿");}};public static final Light3 YELLOW = new Light3("黄"){@Overridepublic void show() {System.out.println("黄");}};private String name;private Light3(String name) {this.name = name;}public String getName() {return name;}public String toString() {return "Light3{" +"name='" + name + '\'' +'}';}public abstract void show();
}

package com.aynu3;public class LightDemo {public static void main(String[] args) {Light r = Light.RED;System.out.println(r);  //com.aynu3.Light@27d6c5e0System.out.println("--------");Light2 r2 = Light2.RED;System.out.println(r2); //Light2{name='红'}System.out.println(r2.getName());   //红r2 = Light2.YELLOW;System.out.println(r2); //Light2{name='黄'}System.out.println(r2.getName());   //黄System.out.println("--------");Light3 r3 = Light3.RED;System.out.println(r3); //Light3{name='红'}System.out.println(r3.getName());   //红r3.show();  //红}
}

com.aynu3.Light@27d6c5e0
--------
Light2{name='红'}
红
Light2{name='黄'}
黄
--------
Light3{name='红'}
红
红

通过enum实现枚举类：

package com.aynu4;public enum Light {RED, GREEN, YELLOW;}

package com.aynu4;public enum Light2 {RED("红"), GREEN("绿"), YELLOW("黄");private String name;private Light2(String name){this.name=name;}public String getName() {return name;}@Overridepublic String toString() {return "Light2{" +"name='" + name + '\'' +'}';}
}

package com.aynu4;public enum Light3 {RED("红"){@Overridepublic void show() {System.out.println("红");}},GREEN("绿"){@Overridepublic void show() {System.out.println("绿");}},YELLOW("黄"){@Overridepublic void show() {System.out.println("黄");}};private String name;private Light3(String name){this.name=name;}public String getName() {return name;}@Overridepublic String toString() {return "Light3{" +"name='" + name + '\'' +'}';}public abstract void show();
}

package com.aynu4;public class LightDemo {public static void main(String[] args) {Light r = Light.RED;System.out.println(r);  //REDSystem.out.println("----------");Light2 r2=Light2.RED;System.out.println(r2);System.out.println(r2.getName());r2 = Light2.YELLOW;System.out.println(r2);System.out.println(r2.getName());System.out.println("----------");Light3 r3= Light3.RED;System.out.println(r3);System.out.println(r3.getName());r3.show();}
}