java枚举：即对java枚举中的例子进行拓展

Posted 2020-10-19

/*
知识点：枚举
    枚举是从java5开始提供的一种新的数据类型，是一个特殊的类，就是多个常量对象的集合
定义格式：
    [修饰符] enum 枚举类名
    {
        常量A, 常量B, 常量C;
    }

*/

//定义枚举
enum Weekday
{
    Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday;
    //枚举类型中的Monday等价于原来的：public static final Weekday Monday = new Weekday();
}

class Employees
{
    private Weekday restday; //一周的哪一天休息（数据类型为Weekday）

    public Weekday getRestday()
    {
        return restday;
    }

    public void setRestday(Weekday restday) //数据类型为Weekday
    {
        this.restday = restday;
    }
}

public class EnumerateExample
{
    public static void main(String[] args) 
    {
        Employees e = new Employees(); //创建员工对象
        e.setRestday(Weekday.Wednesday); //通过类名.对象的方式来设置休息时间
        Weekday restday = e.getRestday(); //用Weekday类型的变量restday来接收得到的值
        
        if(restday == Weekday.Saturday || restday == Weekday.Sunday)
        {
            System.out.println("周末休息...");
        }
        else
        {
            System.out.println("周一至周五休息...");
        }
    }
}

/*
Weekday类的字节码文件内容（用java字节码反编译工具进行反编译后查看）：

final class Weekday extends Enum //自定义的Weekday枚举类在底层里都是继承java.lang中的Enum
{

    public static final Weekday Monday;
    public static final Weekday Tuesday;
    public static final Weekday Wednesday;
    public static final Weekday Thursday;
    public static final Weekday Friday;
    public static final Weekday Saturday;
    public static final Weekday Sunday;
    private static final Weekday $VALUES[];

    public static Weekday[] values()
    {
        return (Weekday[])$VALUES.clone();
    }

    public static Weekday valueOf(String s)
    {
        return (Weekday)Enum.valueOf(Weekday, s);
    }

    private Weekday(String s, int i)
    {
        super(s, i);
    }

    static 
    {
        Monday = new Weekday("Monday", 0);
        Tuesday = new Weekday("Tuesday", 1);
        Wednesday = new Weekday("Wednesday", 2);
        Thursday = new Weekday("Thursday", 3);
        Friday = new Weekday("Friday", 4);
        Saturday = new Weekday("Saturday", 5);
        Sunday = new Weekday("Sunday", 6);
        $VALUES = (new Weekday[] {
            Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday
        });
    }
}
*/