JAVA学习笔记枚举类

Posted 2022-12-01 ！0 ！

1、枚举类的说明

• 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
• 如果枚举类中只一个对象，则可以作为单例模式的实现方式。

2、自定义枚举类

//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 + '\\'' +
                '';
    

3、 jdk 5.0 新增使用enum定义枚举类

//使用enum关键字枚举类
enum Season1 
    //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;

    //2.私化类的构造器,并给对象属性赋值
    private Season1(String seasonName,String seasonDesc)
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    

    //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.、使用enum定义枚举类之后，枚举类常用方法：（继承于java.lang.Enum类）

		Season1 summer = Season1.SUMMER;
        //toString():返回枚举类对象的名称
        System.out.println(summer.toString());

//        System.out.println(Season1.class.getSuperclass());
        System.out.println("****************");
        //values():返回所的枚举类对象构成的数组
        Season1[] values = Season1.values();
        for(int i = 0;i < values.length;i++)
            System.out.println(values[i]);
        
        System.out.println("****************");
        Thread.State[] values1 = Thread.State.values();
        for (int i = 0; i < values1.length; i++) 
            System.out.println(values1[i]);
        

        //valueOf(String objName):返回枚举类中对象名是objName的对象。
        Season1 winter = Season1.valueOf("WINTER");
        //如果没objName的枚举类对象，则抛异常：IllegalArgumentException
//        Season1 winter = Season1.valueOf("WINTER1");
        System.out.println(winter);

5、 枚举类对象分别实现接口

interface Info
    void show();


//使用enum关键字枚举类
enum Season1 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("大约在冬季");
        
    ;