枚举类Java

枚举类

• 类的对象只有有限个，确定的。如：
  • 性别：男、女
  • 季节;春、夏、秋、冬
• 当需要定义一组常量时，强烈建议使用枚举类

如何自定义枚举类

• 方式一：jdk5.0之前，自定义枚举类：

  1声明Season对象的属性:private final修饰

  2.私有化类的构造器,并给对象属性赋值

  3.提供当前枚举类的多个对象：public static final的

  4.其他诉求1：获取枚举类对象的属性

  5.其他诉求2:提供toString()

  public class SeasonTest {
      public static void main(String[] args) {
          Season spring = Season.SPRING;
          System.out.println(spring);
  
      }
  
  }
  //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.私有化类的构造器,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("春天","秋高气爽");
      public static final Season WINTER=new Season("春天","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 + '\'' +
                  '}';
      }
  }
  

如何使用关键字enum定义枚举类

• 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
• 2.声明Season对象的属性:private final修饰
• 3.私有化类的构造器,并给对象属性赋值
• 4.其他诉求1：获取枚举类对象的属性

说明：默认基础class java.lang.Enum类

public class SeasonTest1 {
    public static void main(String[] args) {
        Season1 summer = Season1.SUMMER;
        System.out.println(summer);//SUMMER
        System.out.println(Season1.class.getSuperclass());


    }

}
//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
     WINTER("春天","冰天雪地"),
     SPRING("春天","春暖花开"),
     SUMMER("夏天","夏日炎炎"),
     AUTUMN("春天","秋高气爽");

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


    //3.私有化类的构造器,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;
    }
    }

Enum类的主要方法

• values()方法：返回枚举类型的对象数组。该方法可以很方便地遍历所有的枚举值。

• valueOf(String str)：可以把一个字符串转为对应的枚举类对象。要求字符 串必须是枚举类对象的“名字”。如不是，会有运行时异常：illegalArgumentException。

• toString()：返回当前枚举类对象常量的名称

• public class SeasonTest1 {
      public static void main(String[] args) {
          Season1 summer = Season1.SUMMER;
          //toString()
          System.out.println(summer);//SUMMER
  //      System.out.println(Season1.class.getSuperclass());
          System.out.println("***************");
          Season1[] values = Season1.values();
          for (int i = 0; i <values.length; i++) {
              System.out.println(values[i]);//WINTER SPRING SUMMER AUTUMN
  
          }
          //valueOf(String objName):返回枚举类中对象名是objName的对象,如果没有则抛异常
          Season1 winter = Season1.valueOf("WINTER");
          System.out.println(winter);
  
  
      }
  

实现接口的枚举类

• 情况一：实现接口，在enum类中实现抽象方法

  跟正常类实实现接口一样

情况二：让枚举类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
     WINTER("冬天","冰天雪地"){
        @Override
        public void show() {
            System.out.println("冬天");
        }
    },
     SPRING("春天","春暖花开"){
         @Override
         public void show() {
             System.out.println("春天");
         }
     },
     SUMMER("夏天","夏日炎炎"){
         @Override
         public void show() {
             System.out.println("夏天");
         }
     },
     AUTUMN("秋天","秋高气爽"){
         @Override
         public void show() {
             System.out.println("秋天");
         }
     };

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


    //3.私有化类的构造器,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;
    }

public class SeasonTest1 {
    public static void main(String[] args) 
    for (int i = 0; i <values.length ; i++) {
            System.out.println(values[i]);
            values[i].show();

        }
        Season1 winter = Season1.valueOf("WINTER");
        System.out.println(winter);
        winter.show();
        
 }