enum枚举类的说明

1.枚举类的说明:

  • 1.枚举类的理解:类的对象只有有限个,确定的。我们称此类为枚举类
  • 2.当需要定义一组常量时,强烈建议使用枚举类
  • 3.如果枚举类中只一个对象,则可以作为单例模式的实现方式。

2.如何自定义枚举类?步骤:

class Season{
 //1.声明Season对象的属性:private final修饰
 private final String seasonName;
 private final String seasonDesc;

 //2.私化类的构造器,并给对象属性赋值
 private Season(String seasonName,String seasonDesc){
     this.seasonName = seasonName;
     this.seasonDesc = seasonDesc;
 }

 //3.提供当前枚举类的多个对象:public static final的
 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;
 }
 //4.其他诉求1:提供toString()
 @Override
 public String toString() {
     return "Season{" +
             "seasonName='" + seasonName + '\'' +
             ", seasonDesc='" + seasonDesc + '\'' +
             '}';
 }
}

3.jdk 5.0 新增使用enum定义枚举类。步骤:

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");

 //2.声明Season对象的属性:private final修饰
 private final String seasonName;
 private final String seasonDesc;

 //2.私化类的构造器,并给对象属性赋值

 private Season1(String seasonName,String seasonDesc){
     this.seasonName = seasonName;
     this.seasonDesc = seasonDesc;
 }

 //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;
 }

}

4.使用enum定义枚举类之后,枚举类常用方法:(继承于java.lang.Enum类)

     //toString():返回枚举类对象的名称
     System.out.println(summer.toString());

//        System.out.println(Season1.class.getSuperclass());
        System.out.println("****************");
        //values():返回所的枚举类对象构成的数组
        Season1[] values = Season1.values();
        for(int i = 0;i < values.length;i++){
            System.out.println(values[i]);
        }
        System.out.println("****************");
        Thread.State[] values1 = Thread.State.values();
        for (int i = 0; i < values1.length; i++) {
            System.out.println(values1[i]);
        }

    //valueOf(String objName):返回枚举类中对象名是objName的对象。
    Season1 winter = Season1.valueOf("WINTER");
    //如果没objName的枚举类对象,则抛异常:IllegalArgumentException

//        Season1 winter = Season1.valueOf("WINTER1");
        System.out.println(winter);

5.使用enum定义枚举类之后,如何让枚举类对象分别实现接口:

 void show();
}

//使用enum关键字枚举类
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"){
        @Override
        public void show() {
            System.out.println("春天在哪里?");
        }
    },
    SUMMER("夏天","夏日炎炎"){
        @Override
        public void show() {
            System.out.println("宁夏");
        }
    },
    AUTUMN("秋天","秋高气爽"){
        @Override
        public void show() {
            System.out.println("秋天不回来");
        }
    },
    WINTER("冬天","冰天雪地"){
        @Override
        public void show() {
            System.out.println("大约在冬季");
        }
    };
}
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