public class MyLock {

	AtomicBoolean locked = new AtomicBoolean(false);

	ThreadLocal<Boolean> threadLocal = new ThreadLocal();

	public void lock() {
		while (true) {
			if (locked.compareAndSet(false, true)) {
				threadLocal.set(true);
				return;
			}
		}
	}

	public void unLock() {
		if (threadLocal.get()) {
			locked.compareAndSet(true, false);
		}
	}

}

class Main {

	public static void main(String[] args) {
		MyLock myLock = new MyLock();
		new MyThread(myLock).start();
		new MyThread(myLock).start();
	}
}

class MyThread extends Thread {

	final MyLock myLock;

	MyThread(MyLock myLock) {
		this.myLock = myLock;
	}

	@Override public void run() {
		myLock.lock();
		System.out.println("start - " + Thread.currentThread().getName());
		try {
			Thread.sleep(5000);
		} catch (InterruptedException e) {
			e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
		}
		System.out.println("finish - " + Thread.currentThread().getName());
		myLock.unLock();
	}
}

if (Thread.currentThread() != getExclusiveOwnerThread())

      public static void main(String[] args) {
		MyLock myLock = new MyLock();
		for (int i=0;i<10;i++)
			new MyThread(myLock).start();
	}

threadLocal.set(false);