Java枚举类

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");
}
};
}