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public final class Race {
  private final Vector<Racer> racers;
  private final Object lock = new Object();
  
  public Race(Vector<Racer> racer) {
    racers = (Vector<Racer>) racer.clone(); 
  }
  
  public boolean addRacer(Racer racer){	  
    synchronized(racers.elementAt(racers.size() - 1)) {
      return racers.add(racer);
    }
  }
  
  public boolean removeRacer(Racer racer) {
    synchronized(racers.elementAt(racers.indexOf(racer))) { 
      return racers.remove(racer);      
    }
  }
  
  private double getAverageCurrentSpeed(int i, double currentSpeed) { 
    if (i > racers.size()) {
      return currentSpeed / racers.size();
    }
    synchronized(racers.elementAt(i)) {
      currentSpeed += racers.get(i).getCurrentSpeed();
      return getAverageCurrentSpeed(++i, currentSpeed);  
 	 	  }
  }

  private double getAverageCurrentDistance(int i, double distance) { 
    if (i <= -1) {		 
      return distance / racers.size();
    }     
    synchronized(racers.elementAt(i)) {
      distance += racers.get(i).getDistance();
      return getAverageCurrentDistance(--i, distance);	
    }
  }
  
  public void getStatisticsAtSomePointInRace() {
    synchronized(racerslock) {
      getAverageCurrentSpeed(0, 0.0);
      getAverageCurrentDistance(racers.size()-1, 0.0);
    }
  }
}

public final class Race {
  private final Vector<Racer> racers;
  private final Object privatelock final= Vector<Racer>new racersObject();
  
  public Race(Vector<Racer> racer) {
    racers = (Vector<Racer>) racer.clone(); 
  }
  
  public boolean addRacer(Racer racer){	  
    return racers.add(racer);
  }
  
  public boolean removeRacer(Racer racer) {
    synchronized(racers.elementAt(racers.indexOf(racer))) { 
      return racers.remove(racer);      
    }
  }
  
  private double getAverageCurrentSpeed(int i, double currentSpeed) { 
    if (i > racers.size()) {
      return currentSpeed / racers.size();
    }
    synchronized(racers.elementAt(i)) {
      currentSpeed += racers.get(i).getCurrentSpeed();
      return getAverageCurrentSpeed(++i, currentSpeed);  
 	 	  }
  }

  private double getAverageCurrentDistance(int i, double distance) { 
    if (i > racers.size()) {		 
      return distance / racers.size();
    }     
    synchronized(racers.elementAt(i)) {
      distance += racers.get(i).getDistance();
      return getAverageCurrentDistance(++i, distance);	
    }
  }
  
  public void getStatisticsAtSomePointInRace() {
    synchronized(racerslock) {
      getAverageCurrentSpeed(0, 0.0);
      getAverageCurrentDistance(0, 0.0);
    }
  }
}