Java-枚举类

2022.02.15枚举类

1.自定义枚举类

①JDK1.5之前：自定义枚举类

//自定义枚举类:私有化定义常量
class Season{

    private final String seasonName;
    private final String seasonDesc;

    //私有化构造器初始化对象
    private Season(String seasonName, String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    //提供当前枚举类的多个对象
    public static final Season SPRING = new Season("Spring","Describe1");
    public static final Season SUMMER = new Season("Summer","Describe2");
    public static final Season AUTUMN = new Season("Autumn","Describe3");
    public static final Season WINTER = new Season("Winter","Describe4");

    public String getSeasonName() {
        return seasonName;
    }

    public String getSeasonDesc() {
        return seasonDesc;
    }

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

}

②JDK1.5之后：自定义枚举类

• 使用 enum 定义的枚举类默认继承了 java.lang.Enum类，因此不能再 继承其他类
• 枚举类的构造器只能使用 private 权限修饰符 ?枚举类的所有实例必须在枚举类中显式列出(, 分隔 ; 结尾)。列出的 实例系统会自动添加 public static final 修饰
• 必须在枚举类的第一行声明枚举类对象

public enum SeasonEnum {
SPRING("春天","春风又绿江南岸"),
SUMMER("夏天","映日荷花别样红"),
AUTUMN("秋天","秋水共长天一色"),
WINTER("冬天","窗含西岭千秋雪");
private final String seasonName;
private final String seasonDesc;
private SeasonEnum(String seasonName, String seasonDesc) {
this.seasonName = seasonName;
this.seasonDesc = seasonDesc;
}
public String getSeasonName() {
return seasonName;
}
public String getSeasonDesc() {
return seasonDesc;
}
}

2.Enum类的主要方法：

• 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