java枚举类笔记

1.枚举类Enum

自定义枚举类（不使用enum关键字）

import org.junit.Test;

public class EnumTest {
    
    
    @Test
    public void test(){
    
    
        Season season = Season.AUTUMN;
        System.out.println(season);

    }

}

//自定义枚举类
class Season{
    
    
    public final String seasonName;
    public final String seasonDesc;

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

    public static final Season SPRING = new Season("春天","春天到了");
    public static final Season SUMMER = new Season("夏天","夏天到了");
    public static final Season AUTUMN = new Season("秋天","秋天到了");
    public static final Season WINTER = new Season("冬天","冬天到了");

    public String getSeasonName() {
    
    
        return seasonName;
    }

    public String getSeasonDesc() {
    
    
        return seasonDesc;
    }

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

使用enum关键字：注意：所有使用enum关键字去定义的枚举类，都继承了java.lang.Enum这个类

import org.junit.Test;

public class EnumTest {
    
    
    @Test
    public void test(){
    
    
        Season1 season = Season1.AUTUMN;
        System.out.println(season);

    }

}

//自定义枚举类
enum Season1{
    
    
    //枚举类之间对象用逗号隔开，声明方式也变成这样比较简洁的方式
    SPRING("春天","春天到了"),
    SUMMER("夏天","夏天到了"),
    AUTUMN("秋天","秋天到了"),
    WINTER("冬天","冬天到了");

    public final String seasonName;
    public final String seasonDesc;

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


    public String getSeasonName() {
    
    
        return seasonName;
    }

    public String getSeasonDesc() {
    
    
        return seasonDesc;
    }
    
}

Enum类常用方法

//返回枚举类所有值的一个数组
        Season1[] values = Season1.values();

        for (Season1 season1: values) {
    
    
            System.out.println(season1);
        }

        //返回给定名称的一个枚举类的值,没有就抛异常
        Season1 winter = Season1.valueOf("WINTER");
        System.out.println(winter);

枚举类继承接口

如果该接口对于枚举类中的每一个枚举对象，都相同，就是方法是通用的，那么可以直接写到枚举类内部。如下代码，这时候，每一个枚举类对象调用show都会输出同一句话

interface Info{
    
    
    void show();
}
enum Season1 implements Info{
    
    
    
    //枚举类之间对象用逗号隔开，声明方式也变成这样比较简洁的方式
    SPRING("春天","春天到了"),
    SUMMER("夏天","夏天到了"),
    AUTUMN("秋天","秋天到了"),
    WINTER("冬天","冬天到了");
    
    @Override
    public void show() {
    
    
        System.out.println("这是一个季节");
    }
}

但是枚举类可以让每一个对象实现定制的方法，每个类都实现一次需要实现的接口，这样在方法调用的时候，每个对象调用的就是自己实现的接口

interface Info{
    
    
    void show();
}

//自定义枚举类
enum Season1 implements Info{
    
    

    //枚举类之间对象用逗号隔开，声明方式也变成这样比较简洁的方式
    SPRING("春天","春天到了"){
    
    
        @Override
        public void show() {
    
    
            System.out.println("这是春天");
        };
    },
    SUMMER("夏天","夏天到了"){
    
    
        @Override
        public void show() {
    
    
            System.out.println("这是夏天");
        };
    },
    AUTUMN("秋天","秋天到了"){
    
    
        @Override
        public void show() {
    
    
            System.out.println("这是秋天");
        };
    },
    WINTER("冬天","冬天到了"){
    
    
        @Override
        public void show() {
    
    
            System.out.println("这是冬天");
        };
    };