Expert: Jeff Laatsch - 2/10/2012

Question
QUESTION: I am having a hard time trying to figure out how to lock an object. I have three classes. I have a watertreatment class, station class, and a pipe class. I've created all three of my classes. The watertreatment class is the driver class, the stations are the threads, and the pipes are the lockable object. So my question is how do I set up my pipe class so that each station object that I create can lock it and then unlock it? Right now I am creating the station and pipe objects in the watertreatmant class in a for loop.

ANSWER: Debra,

I could write a book on how this is down, but better yet I was able find you something on-line:

http://docs.oracle.com/javase/tutorial/essential/concurrency/newlocks.html

Good luck,
Jeff


---------- FOLLOW-UP ----------

QUESTION: Thank you sir. I've actually taken a look at that several times but I'm still confused on how to implement it into my program. What I am thinking is that I should have a method in my Pipe class that locks a pipe and then call that in my Station class. For instance:

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;


public class Pipe()

private int number = 0;
private final Lock lock = new ReentrantLock();


   public Pipe()


      public void lock(){
         
try{
lock.lock();}finally{lock.unlock()};
}

Am I going in the right direction with that idea? Would i then be able to call a pipe object from the station class?

Answer
Debra,

Looks good except I am unsure of:

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;


public class Pipe()

private int number = 0;
private final Lock lock = new ReentrantLock();


  public Pipe()


     public void lock(){
        
try{
lock.lock();}finally{lock.unlock()};
}

The 'private' aspects you may want to remove private and then try it.

Good luck,
Jeff