 
      
    
       
      
    
       
      
    
      fast way to add an observer
fast way to add an observer
want to observe current source
the source
 
      
    
       
      
    
       
      
    
       
      
    
      add an observer to the source
add an observer to the source
want observe this source
false if the observer currently observe the source true otherwise
 
      
    
       
      
    
      remove an observer to the source
remove an observer to the source
want to stop observer this source
false if the observer currently doesn't observer the source true otherwise
 
      
    
       
      
    
       
      
    
       
      
    
       
      
    
       
      
    
       
      
    
      notify all the observer
 
      
    
       
      
    
       
      
    
      the observers attached to current source
 
      
    
       
      
    
       
      
    
       
      
    
       
      
    
       
      
    
      (Since version ) see corresponding Javadoc for more information.
the order of notification to observer isn't preserved