ReadWrite Lock

class DemonstrationOfReadWriteLock {
  public static void main(String[] args) throws InterruptedException {
    ReadWriteLock lock = new ReadWriteLock();

    Thread writer1 =
        new Thread(
            () -> {
              try {
                System.out.println("Writer 1 Attempting to acquire write lock");
                lock.acquireWriteLock();
                System.out.println("Writer 1 Acquired write lock");
              } catch (InterruptedException e) {

              }
            });

    Thread writer2 =
        new Thread(
            () -> {
              try {
                System.out.println("Writer 2 Attempting to acquire write lock");
                lock.acquireWriteLock();
                System.out.println("Writer 2 Acquired write lock");
              } catch (InterruptedException e) {

              }
            });

    Thread writer3 =
        new Thread(
            () -> {
              try {
                System.out.println("Writer 3 Attempting to release write lock");
                lock.releaseWriteLock();
                System.out.println("Writer 3 Released write lock");
              } catch (InterruptedException e) {

              }
            });

    Thread reader1 =
        new Thread(
            new Runnable() {
              @Override
              public void run() {
                try {
                  System.out.println("Reader 1 Attempting to acquire read lock");
                  lock.acquireReadLock();
                  System.out.println("Reader 1 Acquired read lock");
                } catch (InterruptedException e) {

                }
              }
            });

    Thread reader2 =
        new Thread(
            () -> {
              try {
                System.out.println("Reader 2 Attempting to release read lock");
                lock.releaseReadLock();
                System.out.println("Reader 2 Released read lock");
              } catch (InterruptedException e) {

              }
            });

    reader1.start();
    Thread.sleep(100);

    writer1.start();
    Thread.sleep(100);

    reader2.start();

    reader1.join();
    reader2.join();
    Thread.sleep(100);

    writer2.start();
    Thread.sleep(100);

    writer3.start();
    Thread.sleep(100);

    writer1.join();
    writer2.join();
    writer3.join();
  }
}

class ReadWriteLock {
  private int readers = 0;
  private boolean writer = false;

  public synchronized void acquireReadLock() throws InterruptedException {
    while (writer) {
      wait();
    }
    readers++;
  }

  public synchronized void releaseReadLock() throws InterruptedException {
    readers--;
    notify();
  }

  public synchronized void acquireWriteLock() throws InterruptedException {
    while (writer || readers > 0) {
      wait();
    }
    writer = true;
  }

  public synchronized void releaseWriteLock() throws InterruptedException {
    writer = false;
    notifyAll();
  }
}