Avoiding Deadlocks

• When you use a reentrant lock, you must create a condition object for which to wait
• Example: to manage "space available" condition
  

  private Lock queueLock = new ReentrantLock();
  private Condition spaceAvailableCondition
     = queueLock.newCondition();
  

• Call await when condition is not fulfilled:
  

  public void add(E newValue)
  {
     . . .
     while (size == elements.length)
        spaceAvailableCondition.await();
     . . .
  }

A waiting thread is blocked until another thread calls signallAll or signal on the condition object for which the thread is waiting.