枚举类基础复习

• 枚举类
• • 1、理解枚举类
  • 2、定义枚举类
  • • 2.1、自定义枚举类（jdk5.0之前）
    • 2.2、enum关键字（jdk5.0之后）
  • 3、Enum类中常用方法
  • 4、枚举类与接口的运用

• 类的对象只有有限个或者说确定个数
• 也可以理解为枚举类定义了一组常量
• 如果枚举类中只有一个对象，则可以作为单例模式的实现方式

public class EnumTest {
    public static void main(String[] args) {
        Season season = Season.SPRING;
        String seasonName = season.getSeasonName();
        System.out.println(season);
        System.out.println(seasonName);
    }
}
//自定义枚举类
class Season{
    private final String seasonName;
    private final String seasonDesc;

    public Season(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    public static final Season SPRING = new Season("春天","春暖花开");
    public static final Season SUMMER = new Season("夏天","夏日福利");
    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");

    //返回某一属性值
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

    @Override
    public String toString() {
        return "Season{" +
                "seasonName='" + seasonName + ''' +
                ", seasonDesc='" + seasonDesc + ''' +
                '}';
    }
}

分析：

• 自定义Season 枚举类，并定义了四个枚举对象SPRING SUMMER AUTUMN WINTER
• 可以为每个枚举对象附加相应的属性值，并且能够根据某个枚举对象获取对应的属性值（根据应用需要）
• 这里只需要理解就行（一般不使用这种）

package com.mtf.枚举;

public class EnumTest01 {
    public static void main(String[] args) {
        Season1 season1 = Season1.SPRING;
        System.out.println(season1);

        //获取定义的枚举类的父类：输出可以看出父类为Enum类
      System.out.println(Season1.class.getSuperclass());
    }
}

//使用enum关键字定义枚举类
enum Season1{

    SPRING("春天","春暖花开"),
    SUMMER("夏天","夏日福利"),
    AUTUMN("秋天","秋高气爽"),
    WINTER("冬天","冰天雪地");

    private final String seasonName;
    private final String seasonDesc;

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


    //返回某一属性值
    public String getSeason1Name() {
        return seasonName;
    }

    public String getSeason1Desc() {
        return seasonDesc;
    }
}

package com.mtf.枚举;

public class EnumMethod {
    public static void main(String[] args) {
        Season1 season1 = Season1.SPRING;
        String name = season1.name();
        System.out.println(season1.toString());

        //values()
        Season1[] values = Season1.values();
		
      //SPRING，SUMMER，AUTUMN，WINTER
        for (int i = 0; i < values.length; i++) {
            System.out.println(values[i]);
        }

        //valueOf(String ObjectName)
        Season1 spring = Season1.valueOf("SPRING");
        //java.lang.IllegalArgumentException：枚举类中没有相应的枚举对象会报错
        Season1 spring1 = Season1.valueOf("SPRING1");
        System.out.println(spring1);
    }
}

分析：

• values() 方法：返回的是枚举类的所有枚举对象
• toString() 方法：返回的是枚举名称（一个枚举对象的名称）
• valueOf(Object obj) 方法：根据相应的枚举名称返回对应的枚举对象

package com.mtf.枚举;

public class EnumInterface {
    public static void main(String[] args) {
        Season2 spring = Season2.SPRING;
        spring.show();
    }
}

interface Info{
    void show();
}


//使用enum关键字定义枚举类
enum Season2 implements Info{

    SPRING("春天","春暖花开"){
        @Override
        public void show() {
            System.out.println("春天在哪里");
        }
    },
    SUMMER("夏天","夏日福利") {
        @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");
        }
    };

    private final String seasonName;
    private final String seasonDesc;

    private Season2(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }


    //返回某一属性值
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

    @Override
    public String toString() {
        return "Season2{" +
                "seasonName='" + seasonName + ''' +
                ", seasonDesc='" + seasonDesc + ''' +
                '}';
    }


}

分析：

• 上述代码实现了枚举类实现接口并重写了接口中的方法（用到了匿名内部类）