您好，在以下代码中，请问this.day=day 在下面是什么意思?

Question

public enum WeekDay { Mon("Monday"), Tue("Tuesday"), Wed("Wednesday"), Thu("Thursday"), Fri( "Friday"), Sat("Saturday"), Sun("Sunday"); /**定义枚举类型自己的属性**/ private final String day; private WeekDay(String day) { this.day = day; } /**定义枚举类型自己的方法**/ public static void printDay(int i){ switch(i){ case 1: System.out.println(WeekDay.Mon); break; case 2: System.out.println(WeekDay.Tue);break; case 3: System.out.println(WeekDay.Wed);break; case 4: System.out.println(WeekDay.Thu);break; case 5: System.out.println(WeekDay.Fri);break; case 6: System.out.println(WeekDay.Sat);break; case 7: System.out.println(WeekDay.Sun);break; default:System.out.println("wrong number!"); } } public String getDay() { return day; } }