Help with concurrency design

Question

I have a situation similar to the following code where m_array and m_link must be guaranteed to be synchronized. Init will get called by different threads so what is the best way to avoid the deadlock?
public class Foo
private final ReentrantLock m_lock = new ReentrantLock();
private final ArrayList<Integer> m_array = new ArrayList<Integer>();
private final LinkedList<Integer> m_list = new LinkedList<Integer>();
private final int m_id = 1;
public void init( final Statement statement, final Foo foo )
m_lock.lock();
try
foo.m_lock();
try
m_array.add( foo.m_id );
m_list.add( foo.m_id );
foo.m_array.add( m_id );
foo.m_list.add( m_id );
finally
foo.m_lock.unlock();
finally
m_lock.unlock();
Edited by: 806320 on Jan 27, 2011 6:18 AM

Answer 1

806320 wrote:
@YoungWinston -As I mentioned, m_array and m_list must be guaranteed to be in sync. Regardless, Synchronize would not help in anyway with this example, the deadlock occurs no matter which lock mechanism you use.What about this?
public class ListManager<T>
   private final List<List<T>> lists;
   public ListManager(List<T>... lists) {
      this.lists = new ArrayList<List<T>>(lists.length);
      for(List<T> list : lists) {
         this.lists.add(list);
   public synchronized boolean add(T value) {
      for (List<T> list : this.lists) {
         list.add(value);
      return true;
   ... other update methods implemented similarly.
}You'd probably want to make sure that the supplied lists are empty, and if you want to be sure that they can't be updated outside the class you'll also have to clone them; but I suspect that's how I'd go about it.
Unless I'm missing something from your original post, I think it does the trick.
With anyone using JDK 1.5+ is there ever a reason to use Synchronize?Absolutely. In fact, I think I'd have to look pretty hard for situations in which I wouldn't use it.
Winston