Need help with Thread Sleep

[bob morkos]

I get the following error, could anyone help?

[error]
java.lang.IllegalMonitorStateException: current thread not owner at java.lang.Object.wait(Native Method) at java.lang.Object.wait(Object.java:420)
[/error]

public class TestSearchTransponderDAO implements Runnable
{
    private boolean foundMatch = false;
    private long transponderId = 0;
    private Thread daoThread = null;
    
    public TestSearchTransponderDAO()
    { 
    }
    
    public TestSearchTransponderDAO(long transponderIdVal)
    { 
      transponderId = transponderIdVal;
    }
    
    public synchronized boolean retrieveTransponderResult(Long transponderId)
    {
        TestSearchTransponderDAO testSearchTransponderDAO = new TestSearchTransponderDAO(transponderId.longValue());
        daoThread = new Thread(testSearchTransponderDAO);
        daoThread.start();
        try {
            // wait for 
            daoThread.wait();
        } catch (InterruptedException e) {
        }
        return foundMatch;
    }
    
 

   public synchronized void run()
   { 
       try
       {
           daoThread.sleep(new Long(50).longValue());
       }
       catch (InterruptedException e)
       {                 
       }
       foundMatch = searchTransponderDAO();   
       daoThread.notify();
 
   }
 
    
    public boolean searchTransponderDAO()
    {
        try
        {                   
          return new Boolean("true").booleanValue();
        }
        catch (TwException e)
        {
            System.out.println(e);
        }
        return new Boolean("false").booleanValue();
    }
    
}

[Ernest Friedman-Hill]

In the method retrieveTransponderResult, you call wait() on the daoThread object, but you're not in a synchronized method of Thread, nor in a block synchronized on that Thread object. To call wait() or notify(), you have to hold the monitor of the object you're calling them on. This is explained in the Javadoc for those methods.

I can't resist pointing out that

return new Boolean("false").booleanValue();

is exactly equivalent in effect to

return false;

except, of course, that it's vastly more expensive computationally.

This is not an advanced Java question, but a beginner's Thread question; I'm moving this to the Threads forum.