Java学习之枚举类

• 枚举类
• • 如何自定义枚举类
  • 如何使用enum 定义枚举类
  • Enum类的主要方法
  • 实现接口的枚举类

枚举的理解：类的对象只有有限个，确定的。
当需要定义一组常量时，强烈建议使用枚举类
方式1. jdk5.0之前，自定义枚举类
方式2. jdk5.0，可以使用enum关键字定义枚举类

public class SeasonTest {
    public static void main(String[] args) {
        String spring = Season.SPRING.getSeasonName();
        System.out.println(spring);  //春天
    }
}

//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","");
    public static final Season SUMMER = new Season("夏天","");
    public static final Season AUTUMN = new Season("秋天","");
    public static final Season WINTER = new Season("冬天","");

    //4. 获取枚举类对象的属性
    public String getSeasonName() {
        return seasonName;
    }
    public String getSeasonDesc() {
        return seasonDesc;
    }

    //5. toString()
    @Override
    public String toString() {
        return "Season{" +
                "seasonName='" + seasonName + ''' +
                ", seasonDesc='" + seasonDesc + ''' +
                '}';
    }
}

使用enum关键字定义枚举类，默认继承java.lang.Enum类

public class SeasonTest2 {
    public static void main(String[] args) {
        Season2 autumn = Season2.AUTUMN;
        System.out.println(autumn.getSeasonName());  //秋天
        System.out.println(autumn.getClass().getSuperclass());  //父类是 java.lang.Enum
    }
}

//使用enum关键字定义枚举类
enum Season2 {
    //1. 提供当前枚举类的对象，多个对象间用‘,’隔开，末尾用';'.
    SPRING("春天", ""),
    SUMMER("夏天", ""),
    AUTUMN("秋天", ""),
    WINTER("冬天", "");
    //2 .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 Season2(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //3. 获取枚举类对象的属性
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }
}

1. values()
2. valueOf(String str)
3. toString()

public class SeasonTest2 {
    public static void main(String[] args) {
        Season2 autumn = Season2.AUTUMN;
        System.out.println(autumn.getSeasonName());  //秋天
        System.out.println(autumn.getClass().getSuperclass());  //父类是 java.lang.Enum

        //values() ： 返回枚举对象数组
        Season2[] values = autumn.values();
        for (int i = 0; i 
            System.out.println(values[i]);  //SPRING  SUMMER  AUTUMN  WINTER
        }

        //valueOf(String str)  ： 找对应枚举对象
        Season2 string = autumn.valueOf("SPRING");
        //Season2 string = autumn.valueOf("XXXX");  //No enum constant ming2.enums.Season2.XXXX
        System.out.println(string);

        //toString()  : 返回当前枚举类对象常量的名称
        System.out.println(autumn.toString());
    }
}

//使用enum定义枚举类
enum Season2 {
    //1. 提供当前枚举类的对象，多个对象间用‘,’隔开，末尾用';'.
    SPRING("春天", ""),
    SUMMER("夏天", ""),
    AUTUMN("秋天", ""),
    WINTER("冬天", "");
    //2 .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 Season2(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //3. 获取枚举类对象的属性
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }
}

1. 实现接口，在enum类中实现抽象方法
2. 让枚举类的对象分别实现接口中的抽象方法

public class SeasonTest2 {
    public static void main(String[] args) {
        Season2 autumn = Season2.AUTUMN;
        autumn.show();  //秋天的show
    }
}

interface info{
    void show();
}
//使用enum定义枚举类
enum Season2 implements info{
    //1. 提供当前枚举类的对象，多个对象间用‘,’隔开，末尾用';'.
    SPRING("春天", ""){
        @Override
        public void show() {
            System.out.println("春天的show");
        }
    },
    SUMMER("夏天", "") {
        @Override
        public void show() {
            System.out.println("夏天的show");
        }
    },
    AUTUMN("秋天", "") {
        @Override
        public void show() {
            System.out.println("秋天的show");
        }
    },
    WINTER("冬天", "") {
        @Override
        public void show() {
            System.out.println("冬天的show");
        }
    };
    //2 .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 Season2(String seasonName, String seasonDesc) {
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //3. 获取枚举类对象的属性
    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }
}

自学笔记，欢迎纠错