java枚举类学习笔记总结

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：

//自定义枚举类
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：

   //使用enum关键字枚举类
      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）

   Season1 summer = Season1.SUMMER;
           //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：
   interface Info{
   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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