如何在Java中自定义排序集

Question

public static void main(String[] args) {
    // TODO Auto-generated method stub
    sortDates(Arrays.asList(new DAY[]{DAY.MON,DAY.WED,DAY.TUE,DAY.THU,DAY.SUN,DAY.SAT,DAY.FRI}));
}
public static void sortDates(List<DAY> dayList){
    Set<DAY> set = new TreeSet<DAY>(dayList);
    for(DAY day : set)
    {
        System.out.println(day);
    }
}
public enum DAY {
    MON("MONDAY"),TUE("TUESDAY"),WED("WEDNESDAY"),THU("THURSDAY"),FRI("FRIDAY"),SAT("SATURDAY"),SUN("SUNDAY");

    private String m_name;

    DAY(String name) {
        m_name=name;
    }
}

这段代码的输出是：周一周二周三周四周五周六周日

但是我想要的输出是这样的SUN MON TUE WED THU FRI SAT

这意味着我想定制排序功能，将星期天移到第一天。

我该怎么做？提前谢谢。

Answer 1

以下方法（使用比较器）需要枚举类中的标识符：

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class week {

    public static void main(String[] args) {
        Comparator<DAY> myComparator = new Comparator<DAY>() {

            @Override
            public int compare(DAY o1, DAY o2) {
                if (o1.getPrio() == o2.getPrio()) {
                    return 0;
                } else if (o1.getPrio() < o2.getPrio()) {
                    return -1;
                }
                return 1;
            }
        };

        sortDates(Arrays.asList(new DAY[] { DAY.MON, DAY.WED, DAY.TUE, DAY.THU, DAY.FRI, DAY.SUN, DAY.SAT }),
                myComparator);

    }

    public static void sortDates(List<DAY> dayList, Comparator<DAY> comparator) {
        Set<DAY> setd = new TreeSet<DAY>(comparator);
        setd.addAll(dayList);

        Set<DAY> set = new TreeSet<DAY>(dayList);
        for (DAY day : set) {
            System.out.println(day);
        }
        System.out.println("comparator:");
        for (DAY day : setd) {
            System.out.println(day);
        }
    }

    public enum DAY {
        MON("MONDAY", 1), TUE("TUESDAY", 2), WED("WEDNESDAY", 3), THU("THURSDAY", 4), FRI("FRIDAY", 5), SAT("SATURDAY",
                6), SUN("SUNDAY", 0);

        private final String m_name;
        private final int prio;

        DAY(String name, int prio) {
            m_name = name;
            this.prio = prio;
        }

        public int getPrio() {
            return prio;
        }
    }

}

Answer 2

@Marco13的答案是迄今为止最正确的：您需要一个自定义比较器来执行您的排序。

幸运的是，谷歌番石榴有一个实用工具：订购。显式（）。

private static Comparator<DAY> AM_ORD = Ordering.explicit(DAY.Sun, ... DAY.Sat);
private static Comparator<DAY> EU_ORD = Ordering.explicit(DAY.Mon, ... DAY.Sun);

public static void sortDates(List<DAY> dayList, boolean am)
{
    Set<DAY> set = new TreeSet<DAY>(am ? AM_ORD : EU_ORD);
    set.addAll(dayList);
    for (DAY day : set)
    {
        System.out.println(day);
    }
}

Answer 3

试试这个。

    import java.util.*;

public class SortDays {


     public static void main(String[] args) {
         // TODO Auto-generated method stub
         sortDates(Arrays.asList(new DAY[]{DAY.MON,DAY.WED,DAY.TUE,DAY.THU,DAY.SUN,DAY.SAT}));
     }
     public static void sortDates(List<DAY> dayList){
         Collections.sort(dayList, new Comparator<DAY>() {
                public int compare(DAY day1, DAY day2) {
                    return day1.getWeight() - day2.getWeight();
                }});
         System.out.println("sortedlist is" + dayList.toString());
     }



}

 enum DAY {
     MON("MONDAY", 2) ,TUE("TUESDAY", 3),WED("WEDNESDAY", 4),THU("THURSDAY", 5),FRI("FRIDAY", 6),SAT("SATURDAY", 7),SUN("SUNDAY", 1);

     private String m_name;
     private int m_weight;

     DAY(String name, int weight) {
         m_name=name;
         m_weight = weight;
     }

     public int getWeight() {
         return this.m_weight;
     }
 }