一、枚举类的使用

枚举类的理解：类的对象只有有限个，确定的。我们称此类为枚举类
当需要定义一组常量时，强烈建议使用枚举类
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。

二、如何定义枚举类

方式一：jdk5.0之前，自定义枚举类

/**
 *
 * 自定义枚举类
 * 
 */
public class test01 {
    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：获取枚举类对象的属性
    public String getSeasonName(){
        return seasonName;
    }

    public String getSeasonDesc(){
        return seasonDesc;
    }

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

方式二：jdk5.0，可以使用enum关键字定义枚举类

/**
 *
 * 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
 *
 */
public class test02 {
    public static void main(String[] args) {
        Season2 summer = Season2.SUMMER;
        System.out.println(summer);

        System.out.println(Season.class.getSuperclass());
    }
}

//使用enum关键字
enum Season2{
    //1.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
    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");

    //2.声明Season对象的属性：private final修饰
    private final String seasonName;
    private final String seasonDesc;

    //3.私有类的构造器，并给对象属性赋值
    private Season2(String seasonName, String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //4.其他诉求
    public String getSeasonName(){
        return seasonName;
    }

    public String getSeasonDesc(){
        return seasonDesc;
    }
}

三、Enum类中常用的方法：

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

public class test03 {
    public static void main(String[] args) {
        Season3 summer = Season3.SUMMER;
        //toString
        System.out.println(summer.toString());

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

        //values()
        Season3[] values = Season3.values();
        for(int i = 0; i < values.length; i++){
            System.out.println(values[i]);
        }
        Thread.State[] values2 = Thread.State.values();
        for(int i = 0; i < values2.length; i++){
            System.out.println(values2[i]);
        }

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

        //valueOf(String objName) 如果没找到会报异常
        Season3 winter = Season3.valueOf("WINTER");
        System.out.println(winter);

    }
}
enum Season3{
    //1.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
    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");

    //2.声明Season对象的属性：private final修饰
    private final String seasonName;
    private final String seasonDesc;

    //3.私有类的构造器，并给对象属性赋值
    private Season3(String seasonName, String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //4.其他诉求
    public String getSeasonName(){
        return seasonName;
    }

    public String getSeasonDesc(){
        return seasonDesc;
    }
}

四、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方法
 *
 */
public class test04 {
    public static void main(String[] args) {
        Season4 winter = Season4.WINTER;

        winter.show();
    }
}

interface Info{
    void show();
}

enum Season4 implements Info{
    //1.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
    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("大学在冬季");
        }
    };

    //2.声明Season对象的属性：private final修饰
    private final String seasonName;
    private final String seasonDesc;

    //3.私有类的构造器，并给对象属性赋值
    private Season4(String seasonName, String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //4.其他诉求
    public String getSeasonName(){
        return seasonName;
    }

    public String getSeasonDesc(){
        return seasonDesc;
    }

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

来源：https://www.cnblogs.com/xiaoran991/p/12552619.html

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枚举类型