/* Based on book example on page 178. */

class Sum
{
  private int sum;

  // Why not a constructor this time?  Start at 0.
  public Sum() { sum = 0; }
  public int getSum() { return sum; }
  public void setSum(int sum) { this.sum = sum; }
  public void addSum(int sum) { this.sum += sum; }
}

class Summation implements Runnable
{
  private int upper;
  private Sum sumValue;

  public Summation(int upper, Sum sumValue)
  {
    this.upper = upper;
    this.sumValue = sumValue;
  }

  public void run()
  {
    int sum = 0;
    for (int i = 1; i <= upper; ++i)
    {
      System.out.printf("Thread 1 is adding %d\n", i);
      sum += i;
    }
    sumValue.addSum(sum);
  }
}

// This one will accumulate perfect squares i^2.
class Summation2 implements Runnable
{
  private int upper;
  private Sum sumValue;

  public Summation2(int upper, Sum sumValue)
  {
    this.upper = upper;
    this.sumValue = sumValue;
  }

  public void run()
  {
    int sum = 0;
    for (int i = 1; i <= upper; ++i)
    {
      System.out.printf("Thread 2 is adding %d\n", i*i);
      sum += i*i;
    }
    sumValue.addSum(sum);
  }
}

public class Driver
{
  public static void main(String [] args)
  {
    if (args.length == 0)
    {
      System.err.printf("Need to include upper value as cmd line arg.\n");
      System.exit(1);
    }
    int upper = Integer.parseInt(args[0]);
    if (upper < 0)
    {
      System.err.printf("Argument cannnot be negative.\n");
      System.exit(1);
    }
    Sum sumObject = new Sum();
    Thread t1 = new Thread(new Summation(upper, sumObject));
    Thread t2 = new Thread(new Summation2(upper, sumObject));
    t1.start();
    t2.start();
    try
    {
      t1.join();
      t2.join();
      System.out.printf("The sum for %d is %d\n", upper,
                        sumObject.getSum());
    }
    catch (InterruptedException e)
    {
    }
  }
}