枚举类和注解

一、枚举类的使用

1.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

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。

 

 

二、如何定义枚举类

方式一：jdk5.0之前自定义枚举类

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 String seasonName;
    private final String seasonDesc;

    //2.私有化类的构造器
    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 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","银装素裹");


    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

    //4其他诉求：提供toString

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

 

方式二：jdk5.0时，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
 * @author ldbstart
 * @create 2021-03-09 0:28
 */
public class SeasonTest1 {
    public static void main(String[] args) {
        Season1 summer = Season1.SUMMER;
        System.out.println(summer);

        System.out.println(Season1.class.getSuperclass());
    }

}

enum  Season1{
    //1.要求首先提供当前类的对象，多个对象之间用逗号，隔开，末尾用分号；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","银装素裹");

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

    //3.私有化类的构造器
    private Season1(String seasonName,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //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;
    }

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

 

三、Enum类中的常用方法