enum编译出错,该怎么解决

enum编译出错
直接上代码，一个enum的定义后使用，编译不过，求解
Weeks.java
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package p_179;

public enum Weeks {
MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY
}
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EnumSettest.java
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package p_179;

import java.util.EnumSet;
import p_179.Weeks;

public class EnumSettest {

/**
 * @param args
 */
public static void main(String[] args) {
// TODO Auto-generated method stub
EnumSet<Weeks> week = EnumSet.noneOf(Weeks.class);
week.add(MONDAY);
System.out.println("所有元素" + week);
week.remove(MONDAY);
System.out.println("所有元素" + week);
week.addAll(EnumSet.complementOf(week));
System.out.println("所有元素" + week);
week.removeAll(EnumSet.range(MONDAY, TUESDAY));
System.out.println("所有元素" + week);
}

}
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定义的枚举MONDAY编译不过，提示MONDAY cannot be resolved

------解决方案--------------------

EnumSet<Weeks> week = EnumSet.noneOf(Weeks.class);
		week.add(Weeks.MONDAY);
		System.out.println("所有元素" + week);
		week.remove(Weeks.MONDAY);
		System.out.println("所有元素" + week);
		week.addAll(EnumSet.complementOf(week));
		System.out.println("所有元素" + week);
		week.removeAll(EnumSet.range(Weeks.MONDAY, Weeks.TUESDAY));
		System.out.println("所有元素" + week);