（Java）如何对对象数组进行排序，并断开两个对象之间的联系？

Question

Say I have an object - Team . Team has three fields, wins , losses and draws .

If I have a few objects say Team1 , Team2 , Team3 , where Team1 has 3 wins, 2 losses, and 1 tie, Team2 has 3 wins and 3 losses, and Team3 has 2 wins, 3 losses, and 1 tie.

Put all three teams in an array.

I am trying to sort (I know how to do this.. implement Comparable , override compareTo() use Array.sort ) them by wins, and if two teams have the same wins, I want to then sort them by losses (and eventually a third field will be added to further break ties).

Should I write my own sort method? Can someone point me in the right direction because I have no clue where to go with this.

Answer 1

Similar to Ben's answer, but a bit different, I often use the following pattern for clarity. This is a Comparator , but the code for Comparable would be similar.

Comparator<Team> myComparator = new Comparator() {
   @Override
   public int compare(Team t1, Team t2) {
      int result = t1.getWins() - t2.getWins();
      if (result == 0)
         result = t2.getLosses() - t1.getLosses();
      if (result == 0)
         ... more tests here

      return result;
   }

};

Note that taking the difference of two integers might overflow in extreme cases, so a more robust variation would use Integer.compare(t1.getWins(), t2.getWins()) . However, in this case, it is unlikely that your teams will have more than 2^31 wins or losses. :-)

To use this, go

Arrays.sort(myArrayOfTeams, myComparator);

Answer 2

If you have the good fortune to be using java-8 , then you could just do this:

ArrayList<Team> teams = myTeams();

Collections.sort(teams,
    Comparator.comparingInt(Team::getWins())
              .thenComparingInt(Team::getTies());
    );

Or if you are using an array:

Team[] teams = myTeams();

Arrays.sort(teams,
    Comparator.comparingInt(Team::getWins())
              .thenComparingInt(Team::getTies());
    );

This also makes it easier to sort by other things, such as the team's name.

Answer 3

You need to modify Comparable to not only consider wins, but to consider ties, especially when wins occur.

So in your compareTo, add an if to check when wins are equal, and then inside that if do the check on losses. Here you can even add in the check for draws as well.

Answer 4

In your overridden compareTo() method, you would simply need to catch when the wins are equal and then assign it a preference based on losses so

compareTo(Team other){
    if(this.getWins() > other.getWins()){
        return 1;
    } else if(this.getWins() == other.getWins()){
        if(this.getLosses() < other.getLosses()){
            return 1;
        }
        return -1;
    }
    return -1;
}

You could then add another else if in the inner loop to check if losses are equal, and in that if statement you would compare the ties, and if they are completely equal you would return a 0