java如何比较和排序树集中的项目？

Question

我有一门课叫《玩家与输赢》

public class Player
{
    private String          name ; 
    private int             ranking=0; 
    private int             wins = 0 ;
    private int             lossess = 0 ; 


    private boolean         isPrivate =false; 
    private int             experiance =0; 

public float getWinRatio()
{ 
     if( getExperiance() <= 0 )  return -0.0f ;  
     return  (getWins()/(float)getExperiance()) ;         
}

我有一个有10000个玩家对象的树集。我如何将它们相互比较，然后根据这个赢比函数对它们进行排序

Answer 1

您需要在类中正确地声明方法，以便对其进行编译。但是一旦你这样做了，你就可以像这样把一个Comparator传递给TreeSet

  Set<Player> players = new TreeSet<>(Comparator.comparing(Player::getWinRatio));

在这里，我只是将值添加到树集

      int[] numbs = { 5, 3, 1, 4, 2, 9, 7, 6, 8
      };

      // Integer has a natural ordering in ascending order so no
      // Comparator was needed 
      Set<Integer> set = new TreeSet<>();
      for (int n : numbs) {
         set.add(n);
      }

瞧！它们被分类了

      System.out.println(set);

如果你想按相反的顺序对它们进行排序，你可以这样分配树集

        Set<Integer> set = new TreeSet<>(Comparator.reverseOrder());

对于你的胜利配给排序，你可以像这样颠倒顺序

 Set<Player> players =
            new TreeSet<>(Comparator.comparing(Player::getWinRatio).reversed());

Answer 2

你需要用Comparator创建一个新的TreeSet，它根据winRatio比较玩家。然后，你只需要把玩家从原来的TreeSet复制到新的TreeSet。以下是参考代码：

import java.util.Comparator;
import java.util.TreeSet;

class Player {
    private String name;
    private int ranking = 0;
    private int wins = 0;
    private int lossess = 0;
    private boolean isPrivate = false;
    private int experiance = 0;

    public Player(String name, int ranking, int wins, int lossess, boolean isPrivate, int experiance) {
        super();
        this.name = name;
        this.ranking = ranking;
        this.wins = wins;
        this.lossess = lossess;
        this.isPrivate = isPrivate;
        this.experiance = experiance;
    }

    String getName() {
        return name;
    }

    public int getExperiance() {
        return experiance;
    }

    public int getWins() {
        return wins;
    }

    public float getWinRatio() {
        if (getExperiance() <= 0)
            return -0.0f;
        return (getWins() / (float) getExperiance());
    }

    @Override
    public String toString() {
        return "Player [name=" + name + ", ranking=" + ranking + ", wins=" + wins + ", lossess=" + lossess
                + ", isPrivate=" + isPrivate + ", experiance=" + experiance + "]";
    }
}

class DefaultComparator implements Comparator<Player> {
    @Override
    public int compare(Player p1, Player p2) {
        return p1.getName().compareTo(p2.getName());
    }
}

class PlayerWinRatioComparator implements Comparator<Player> {
    @Override
    public int compare(Player p1, Player p2) {
        return p1.getWinRatio() > p2.getWinRatio() ? 1 : (p1.getWinRatio() == p2.getWinRatio() ? 0 : -1);
    }
}

public class TreeSetExample {
    public static void main(String[] args) {
        TreeSet<Player> original = new TreeSet<Player>(new DefaultComparator());
        original.add(new Player("A", 5, 1, 2, true, 4));
        original.add(new Player("B", 4, 2, 1, false, 5));
        original.add(new Player("C", 2, 3, 2, true, 3));
        original.add(new Player("X", 3, 2, 3, false, 2));
        original.add(new Player("Y", 6, 4, 2, true, 1));
        original.add(new Player("Z", 1, 2, 4, true, 6));

        TreeSet<Player> copy = new TreeSet<Player>(new PlayerWinRatioComparator());

        // Copy the elements of original TreeSet to the copy TreeSet
        for (Player player : original) {
            copy.add(player);
        }

        //Display the elements copy TreeSet
        for (Player player : copy) {
            System.out.println(player);
        }
    }
}

输出：

Player [name=A, ranking=5, wins=1, lossess=2, isPrivate=true, experiance=4]
Player [name=Z, ranking=1, wins=2, lossess=4, isPrivate=true, experiance=6]
Player [name=B, ranking=4, wins=2, lossess=1, isPrivate=false, experiance=5]
Player [name=C, ranking=2, wins=3, lossess=2, isPrivate=true, experiance=3]
Player [name=Y, ranking=6, wins=4, lossess=2, isPrivate=true, experiance=1]