我有两家公司asoft和bsoft的代码。我也不能改变。这是我的情况的简化版本，我敢肯定，它有足够的信息来查找导致问题的原因。

bsoft提供了IGang，它代表可以与其他帮派作战的帮派。

package bsoft;

public interface IGang {
    /** @return negative, 0, or positive, respectively
     *          if this gang is weaker than, equal to, or stronger
     *          than the other
     */
    public int compareTo(IGang g);
    public int getStrength();
    public String getName();
    public void attack(IGang g);
    public void weaken(int amount);
}

asoft提供了GangWar，它允许IGang进行战斗：

package asoft;
import java.util.*;
import bsoft.*;
/** An `IGang` ordered by identity (name) */
public interface ComparableGang extends IGang, Comparable<IGang> {}

package asoft;
import java.util.*;

public class GangWar {
    public final Set<ComparableGang> gangs = new TreeSet<ComparableGang>();
    public void add(ComparableGang g) {gangs.add(g);}
    public void doBattle() {
        while (gangs.size() > 1) {
          Iterator<ComparableGang> i = gangs.iterator();
          ComparableGang g1 = i.next();
          ComparableGang g2 = i.next();
          System.out.println(g1.getName() + " attacks " + g2.getName());
          g1.attack(g2);
          if (g2.getStrength() == 0) {
              System.out.println(g1.getName() + " smokes " + g2.getName());
              gangs.remove(g2);
          }
          if (g1.getStrength() == 0) {
              System.out.println(g2.getName() + " repels " + g1.getName());
              gangs.remove(g1);
          }
        }
        for (ComparableGang g : gangs) {
            System.out.println(g.getName() + " now controls the turf!");
        }
    }
}

它需要Gang您提供给它的s
的附加约束Comparable，大概是它可以按名称排序或避免重复。每个帮派（为简单起见，这里使用任意顺序的Set顺序）都会攻击另一个帮派，直到只剩下一个帮派（如果最后两个有并列，则没有帮派）。我已经编写了一个简单的实现来对其ComparableGang进行测试：

import asoft.*;
import bsoft.*;
import java.util.*;

class Gang implements ComparableGang {
    final String name;
    int strength;

    public Gang(String name, int strength) {
        this.name = name;
        this.strength = strength;
    }

    public String getName() {return name;}
    public int getStrength() {return strength;}

    public int compareTo(IGang g) {
        return strength - g.getStrength();
    }

    public void weaken(int amount) {
        if (strength < amount) strength = 0;
        else strength -= amount;
    }

    public void attack(IGang g) {
        int tmp = strength;
        weaken(g.getStrength());
        g.weaken(tmp);

    }

    public boolean equals(Object o) {
      if (!(o instanceof IGang)) return false;
      return name.equals(((IGang)o).getName());
    }
}

class Main {
   public static void main(String[] args) {
       GangWar gw = new GangWar();
       gw.add(new Gang("ballas", 2));
       gw.add(new Gang("grove street", 9));
       gw.add(new Gang("los santos", 8));
       gw.add(new Gang("triads", 9));
       gw.doBattle();
   }
}

测试出来…

$ java Main
ballas attacks los santos
los santos repels ballas
los santos attacks grove street
grove street repels los santos
grove street now controls the turf!

问题是，三合会不会出现在战斗中。实际上，gangs.size()在doBattle()返回开始处直接打印3而不是4。为什么？如何解决？