Understanding contention examples in developerWorks article

[HanMing Low]

Hi,
I'd appreciate if anyone can help to explain to me why if a thread is executing setUserInfo in the following code will locked out thread of getServiceInfo and setServiceInfo as well.

  
public class AttributesStore {
  private HashMap usersMap = new HashMap();
  private HashMap servicesMap = new HashMap();
  public synchronized void setUserInfo(String user, UserInfo userInfo) {
    usersMap.put(user, userInfo);
  }
  public synchronized UserInfo getUserInfo(String user) {
    return usersMap.get(user);
  }
  public synchronized void setServiceInfo(String service, 
                                          ServiceInfo serviceInfo) {
    servicesMap.put(service, serviceInfo);
  }
  public synchronized ServiceInfo getServiceInfo(String service) {
    return servicesMap.get(service);
  }
}

As explained in an article in
http://www-106.ibm.com/developerworks/java/library/j-threads2.html
Technique 2 : Reducing lock granularity
I appreciate any advice.
Cheers.

Han Ming

[Thomas Thomas]

Hi
u cannot run two synchronized methods of the same object at a time bcz the lock is given by the object and it has only one lock.
if u r using a complex method in which a small part is to be synchronized .u can synchronized blocks
synchronized(this/object){
}
I hope i didn't misunderstand u r question.
thomas

[HanMing Low]

Hi,
Thanks for the reply.
That answers my question.

Cheers.

Han Ming