枚举类笔记

枚举类笔记 枚举 一、基础入门 1.常用范围

一般用于定义一组相类似的常量

2.古老方式定义枚举类

public class TestOne {
    public static void main(String[] args) {
        System.out.println(People.LIU);
        System.out.println(People.LI);
    }
}


class People {
    private final String name;
    private final Integer age;

    People(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public static final People LIU = new People("liu", 12);
    public static final People LI = new People("li", 23);

    @Override
    public String toString() {
        return "People{" +
                "name='" + name + ''' +
                ", age=" + age +
                '}';
    }
}

3.Enum关键字定义 3.1 默认覆盖

public class TestOne {
    public static void main(String[] args) {
        System.out.println(People.LIU);
        System.out.println(People.LI);
        //补充getClass和getDeclaringClass的区别 看getDeclaringClass源码
        System.out.println(People.LI.getDeclaringClass());
        System.out.println(People.LI.getClass());
    }
}


enum People {
    
    LIU("liu",12),
    LI("li",24);

    private final String name;
    private final Integer age;

    People(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public Integer getAge() {
        return age;
    }
    
}

结果图

差异主要看源码，源码如下

    public final Class getDeclaringClass() {
        Class clazz = getClass();
        Class zuper = clazz.getSuperclass();
        return (zuper == Enum.class) ? (Class)clazz : (Class)zuper;
    }

多判定更加稳定

3.2 手动覆盖

    @Override
    public String toString() {
        return "People{" +
                "name='" + name + ''' +
                ", age=" + age +
                '}';
    }

结果图

二、常用方法

1.values()

public class TestOne {
    public static void main(String[] args) {
        System.out.println(People.LIU);
        System.out.println(People.LI);
        //补充getClass和getDeclaringClass的区别 看getDeclaringClass源码
        System.out.println(People.LI.getDeclaringClass());
        System.out.println(People.LI.getClass());
        System.out.println("----------------------------------------");

        for (People value : People.values()) {
            System.out.println(value);
        }
    }
}


enum People {
    
    LIU("liu",12),
    LI("li",24);

    private final String name;
    private final Integer age;

    People(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public Integer getAge() {
        return age;
    }

}

结果图

PS：个人理解，就是通过values()将自定义枚举类变成一个数组

2.valueOf()

很简单…就是在括号内输入想要的对象名，得到该对象

        System.out.println("---------------------------------------");
        People liu = People.valueOf("LIU");
        System.out.println(liu);

结果图

3.toString()

System.out.println("---------------------------------------");System.out.println(People.LI.toString());

结果图

三、接口实现 1.接口实现

public class TestOne {
    public static void main(String[] args) {
        People.valueOf("LIU").show();
        People.valueOf("LI").show();
        People.LIU.show();
        People.LI.show();

        System.out.println(People.LI.getDeclaringClass());
        System.out.println(People.LI.getClass());
    }
}


interface DetailInfo {
    
    void show();
}


enum People implements DetailInfo{
    
    LIU("liu",12){
        @Override
        public void show() {
            System.out.println("溜溜溜");
        }
    },
    LI("li",24) {
        @Override
        public void show() {
            System.out.println("莉莉力");
        }
    };

    private final String name;
    private final Integer age;

    People(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public Integer getAge() {
        return age;
    }

}

2.结果图

这里我们就可以发现，上面我提到的getDeclaringClass和getClass的区别了。

参考：https://www.bilibili.com/video/BV1Kb411W75N?p=502