java 基础 -- 枚举类的简介

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自定义枚举类：

/**
 * @Date: 2018/12/3 11:18
 * @Description: 自定义枚举类
 */
public class testEnum {

    public static void main(String args[]) {

        Season spring = Season.SPRING;
        System.out.println(spring);

    }
}

//自定义枚举类
class Season{

    //1.提供类的属性，声明为 private final
    private final String seasonName;
    private final String seasonDesc;

    //2.声明为final的属性，在构造器中初始化
    private Season(String seasonName ,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //3.通过公共的方法来调用属性
    public String getSeasonName() {
        return seasonName;
    }
    public String getSeasonDesc() {
        return seasonDesc;
    }

    //4.创建枚举类的对象:将类的对象声明 public static final
    private static final Season SPRING= new Season("spring","春暖花开");
    private static final Season SUMMER= new Season("summer","夏日炎炎");
    private static final Season AUTUMN= new Season("autumn","秋高气爽");
    private static final Season WINTER= new Season("winter","白雪皑皑");


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

 若枚举只有一个对象，则可以作为是一种单例模式的实现方式。

使用enum  定义枚举类：

/**
 * @Date: 2018/12/3 11:18
 * @Description:
 *  枚举类
 *  1.如何自定义枚举类
 *  2.如何使用enum 关键字定义枚举类
 *     > 常用的方法
 *     > 如何让枚举类实现接口
 *   values():将枚举类里面的所有的对象以数组的形式返回。
 *   valueof():传入string类型的参数，返回string的对象（返回枚举类的对象）
 */
public class testEnum1 {

    public static void main(String args[]) {

        Season1 spring = Season1.SPRING;
        System.out.println(spring);

        spring.show();

        //1.values()
        Season1[] season1s = Season1.values();
        for (int i=0;i<season1s.length; i++){
            System.out.println(season1s[i]);
        }

        //2.valueof(String name):要求传入的形参name是枚举类对象的名字。
        //否则，报  java.lang.IllegalArgumentException 异常
        String str = "SPRING";
        Season1 season1 = Season1.valueOf(str);
        System.out.println(season1);

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

interface Info{
    void show();
}

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

    SPRING("spring","春暖花开"),
    SUMMER("summer","夏日炎炎"),
    AUTUMN("autumn","秋高气爽"),
    WINTER("winter","白雪皑皑");


    //1.提供类的属性，声明为 private final
    private final String seasonName;
    private final String seasonDesc;

    //2.声明为final的属性，在构造器中初始化
    private Season1(String seasonName ,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //3.通过公共的方法来调用属性
    public String getSeasonName() {
        return seasonName;
    }
    public String getSeasonDesc() {
        return seasonDesc;
    }

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

    public void show(){
        System.out.println("123456789");
    }
}

运行结果：