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copied!<p>Nice question, I have written a small class that will demonstrate how Semaphores can be used to run threads in a sequence. Hope this helps:</p> <pre><code>public class LockingDemo{ private Semaphore a = new Semaphore(0); private Semaphore b = new Semaphore(0); private Semaphore c = new Semaphore(1); class A implements Runnable{ @Override public void run() { try { c.acquire(1); System.out.println("Doing A"); a.release(1); } catch (InterruptedException e) { e.printStackTrace(); } } } class B implements Runnable{ @Override public void run() { try{ a.acquire(1); System.out.println("Doing B"); b.release(1); } catch (InterruptedException e) { e.printStackTrace(); } } } class C implements Runnable{ @Override public void run() { try{ b.acquire(1); System.out.println("Doing C"); c.release(1); } catch (InterruptedException e) { e.printStackTrace(); } } } public void a() throws InterruptedException{ new Thread(new A()).start(); } public void b() throws InterruptedException{ new Thread(new B()).start(); } public void c() throws InterruptedException{ new Thread(new C()).start(); } public static void main(String[] args) throws InterruptedException { LockingDemo ld = new LockingDemo(); System.out.println("FIRST RUN CALLING B -> A -> C"); ld.b(); ld.a(); ld.c(); Thread.currentThread().sleep(2000); System.out.println("SECOND RUN CALLING C -> B -> A"); ld.c(); ld.b(); ld.a(); } } </code></pre> <p>Here is the OUTPUT</p> <pre><code>FIRST RUN CALLING B -> A -> C Doing A Doing B Doing C SECOND RUN CALLING C -> B -> A Doing A Doing B Doing C </code></pre>

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