Judge.java (judge version)

package runners_judge;

import java.util.*;

public class Judge implements Runnable

    {
    private static ArrayList<Runner> chart = new ArrayList<Runner>();

    public static synchronized void addRunner(Runner r)
        {
        if(r.hasArrived())
            chart.add(r);
        if(chart.size() == 1)
            System.out.println(r.toString() + " won the competition!");
        }

    public static synchronized void printChart()
        {
        for(int i = 0; i < chart.size(); i++)
            System.out.println(chart.get(i).toString() + " has reached position " + i);
        }

    public void run()
        {
        synchronized(this)
            {
            while(chart.isEmpty())
                {
                try
                    {
                    wait();
                    }
                catch(InterruptedException e)
                    {
                    e.printStackTrace();
                    }
                }
            }
        }
    }