Package com.day.util

Class ListenerList

java.lang.Object
com.day.util.ListenerList
public class ListenerList extends Object
The ListenerList class provides a utility to maintain lists of registered listeners. It is fairly lightweight and should not impose to much memory overhead.

Use the getListeners() method when notifying listeners. Note that no garbage is created if no listeners are registered. The recommended code sequence for notifying all registered listeners of say, FooListener.eventHappened, is: 

 Object[] listeners = myListenerList.getListeners();
 for (int i = 0; i < listeners.length; ++i) {
    ((FooListener) listeners[i]).eventHappened(event);
 }
Since:
iguana

  • Constructor Summary

    Constructors
    Constructor
    Description
    ListenerList()
    Creates an instance of this listener list class.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    addListener(Object listener)
    Adds a listener to the list of listeners if it is not yet registered in the list.
    void
    clear()
    Clears the list of registered listeners.
    Object[]
    getListeners()
    Returns the list of registered listeners.
    Object[]
    getListeners(Class requestedType)
    Returns the list of registered listeners in an array of the reqeusted runtime type.
    boolean
    removeListener(Object listener)
    Removes a listener from the list of listeners if it is contained.
    int
    size()
    Returns the number of currently registered listeners.

    Methods inherited from class java.lang.Object

    equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • ListenerList

      public ListenerList()
      Creates an instance of this listener list class.

  • Method Details

    • addListener

      public boolean addListener(Object listener)
      Adds a listener to the list of listeners if it is not yet registered in the list.
      Parameters:
      listener - The listener to add to the list. If null nothing is done.
      Returns:
      true if the listener has been added to the list

    • removeListener

      public boolean removeListener(Object listener)
      Removes a listener from the list of listeners if it is contained.
      Parameters:
      listener - The listener to remove from the list. If null nothing is done.
      Returns:
      true if the listener has been added to the list

    • clear

      public void clear()
      Clears the list of registered listeners.

    • size

      public int size()
      Returns the number of currently registered listeners.
      Returns:
      the size

    • getListeners

      public Object[] getListeners()
      Returns the list of registered listeners. Note that this method returns the same array for two subsequent calls if no listeners have been added or removed in the mean time. This also means, that callers of this method MUST NOT modify the array returned.
      Returns:
      the listeners

    • getListeners

      public Object[] getListeners(Class requestedType)
      Returns the list of registered listeners in an array of the reqeusted runtime type. Note that this method returns the same array for two subsequent calls if no listeners have been added or removed in the mean time and if the element type of is assignment compatible. This also means, that callers of this method MUST NOT modify the array returned.
      Parameters:
      requestedType - The runtime type of the components of the array to return.
      Returns:
      the listeners
      Throws:
      ArrayStoreException - if the runtime type is not a supertype of the runtime type of every element in this list.