public class EvenOddPrinter {
  private volatile boolean odd = false;
  private int count = 1;
  private int MAX = 20;

  public void printOdd() {
    synchronized (this) {
      while (!odd) {
        try {
          wait();
        } catch (InterruptedException ie) {
          ie.printStackTrace();
        }
        System.out.println("Odd Thread :" + count);
        count++;
        if (count == MAX) return;
        odd = false;
        notify();
      }
    }
  }

  public void printEven() {
    synchronized (this) {
      while (odd) {
        try {
          wait();
        } catch (InterruptedException ie) {
          ie.printStackTrace();
        }
        System.out.println("Even Thread :" + count);
        count++;
        if (count == MAX) return;
        odd = true;
        notify();
      }
    }
  }
}

public class PrintThread implements Runnable {
  private EvenOddPrinter printer;
  private String evenOddString;

  public PrintThread(EvenOddPrinter printer, String evenOddString) {
    this.printer = printer;
    this.evenOddString = evenOddString;
  }

  @Override
  public void run() {
    if (evenOddString.equalsIgnoreCase("odd")) printer.printOdd();
    else printer.printEven();
  }
}

public class TesPrintEvenOdd {
  public static void main(String[] args) {
    EvenOddPrinter printer = new EvenOddPrinter();
    Thread th1 = new Thread(new PrintThread(printer, "Odd"));
    Thread th2 = new Thread(new PrintThread(printer, "Even"));
    th1.start();
    th2.start();
  }
}