java枚举类

说明

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，建议使用枚举类。

自定义枚举类

1. 步骤
   1）声明枚举类对象的属性：private final修饰。
   2）私有化类的构造器，并且给对象属性赋值。
   3）提供枚举类的多个对象：public static final修饰。
2. 举例

class Season{
    private final String seasonName;
    private final String seasonDesc;

    private Season(String seasonName,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }

    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");
}

enum定义枚举类

1. 步骤
   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。
   2）声明枚举类对象的属性：private final修饰。
   3）私有化类的构造器，并给对象属性赋值。
2. 举例

enum Season {
    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");

    private final String seasonName;
    private final String seasonDesc;

    private Season1(String seasonName,String seasonDesc){
        this.seasonName = seasonName;
        this.seasonDesc = seasonDesc;
    }
}

使用enum定义枚举类之后，枚举类常用方法

1. toString()：返回枚举类对象的名称。
2. values()：返回所有的枚举类对象构成的数组。
3. valueOf(String objName)：返回枚举类中对象名是objName的对象。
   举例：

Season summer = Season.SUMMER;

System.out.println(summer.toString());//SUMMER

Season[] values = Season.values();
for(int i = 0;i < values.length;i++){
   System.out.println(values[i]);//SPRING  SUMMER AUTUMN  WINTER
}
Season spring = Season.valueOf("SPRING");
//如果没objName的枚举类对象，则抛异常：IllegalArgumentException
System.out.println(spring );//SPRING

使用enum定义枚举类之后，枚举类对象实现接口

interface Info{
    void show();
}

enum Season implements Info{
    SPRING("春天","春暖花开"){
        @Override
        public void show() {
            System.out.println("春天");
        }
    },
    SUMMER("夏天","夏日炎炎"){
        @Override
        public void show() {
            System.out.println("夏天");
        }
    },
    AUTUMN("秋天","秋高气爽"){
        @Override
        public void show() {
            System.out.println("秋天");
        }
    },
    WINTER("冬天","冰天雪地"){
        @Override
        public void show() {
            System.out.println("冬天");
        }
    };
}