枚举类

Posted 2021-07-25 高高for 循环

枚举类的理解：

1. 类的对象只有有限个，确定的。我们称此类为枚举类
2. 当需要=定义一组常量时，强烈建议使用枚举类
3. 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。

如何定义枚举类

• 方式一：jdk5.0之前，自定义枚举类
• 方式二：jdk5.0，可以使用enum关键字定义枚举类

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
   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("秋天","秋高气爽");
    public static final Season WINTER = new Season("冬天","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 + '\\'' +
                '}';
    }
}

补充:

变量 : https://blog.csdn.net/weixin_48052161/article/details/115800936

使用enum关键字定义枚举类

说明：

定义的枚举类 默认继承于java.lang.Enum类

java.lang.Enum重写了toString方法

案例:

注意:

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.

package com.cy.enum1;

public class SeasonTest1 {

    public static void main(String[] args) {
        Season1 winter = Season1.WINTER;
        System.out.println(winter);
    }

}


enum Season1{

    SPRING("春天","春暖花开"),
    SUMMER("夏天","夏日炎炎"),
    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;
    }


    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }
    
//    //4.其他诉求1：提供toString()
//
//    @Override
//    public String toString() {
//        return "Season1{" +
//                "seasonName='" + seasonName + '\\'' +
//                ", seasonDesc='" + seasonDesc + '\\'' +
//                '}';
//    }

}

Enum类中的常用方法：

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

案例:

package com.cy.enum1;

public class SeasonTest1 {

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


        System.out.println("****************");

        Season1[] values = Season1.values();
        for(int i = 0;i < values.length;i++){
            System.out.println(values[i]);

        }
        
        System.out.println("****************");
        Season1 winter = Season1.valueOf("WINTER1");
        System.out.println(winter);

    }

}


enum Season1{

    SPRING("春天","春暖花开"),
    SUMMER("夏天","夏日炎炎"),
    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;
    }


    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

}

另: 打印线程Thread的State状态

State作为Thread的内部内类 定义为枚举类

public class SeasonTest1 {

    public static void main(String[] args) {

        Thread.State[] values1 = Thread.State.values();
        for (int i = 0; i < values1.length; i++) {
            System.out.println(values1[i]);
        }

    }

}

使用enum关键字定义的枚举类实现接口的情况

• 情况一：实现接口，在enum类中实现抽象方法
• 情况二：让枚举类的对象分别实现接口中的抽象方法

案例:

package com.cy.enum1;

public class SeasonTest1 {

    public static void main(String[] args) {

        Season1[] values = Season1.values();
        for (Season1 season1 :values){
            System.out.println(season1);
            season1.show();
        }

    }

}

interface  info {
    void  show();
}


enum Season1 implements  info{

    SPRING("春天","春暖花开"){
        @Override
        public void show() {
            System.out.println("春天在哪里？");
        }
    },
    SUMMER("夏天","夏日炎炎"){
        @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 Season1(String seasonName,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }


    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

    // @Override
    // public void show() {
    //     System.out.println("这是一个季节");
    // }
}