Class ListenerList<E>
- java.lang.Object
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- org.eclipse.core.runtime.ListenerList<E>
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- Type Parameters:
E
- the type of listeners in this list
- All Implemented Interfaces:
Iterable<E>
public class ListenerList<E> extends Object implements Iterable<E>
This class is a thread safe list that is designed for storing lists of listeners. The implementation is optimized for minimal memory footprint, frequent reads and infrequent writes. Modification of the list is synchronized and relatively expensive, while accessing the listeners is very fast. For legacy code, readers are given access to the underlying array data structure for reading, with the trust that they will not modify the underlying array.A listener list handles the same listener being added multiple times, and tolerates removal of listeners that are the same as other listeners in the list. For this purpose, listeners can be compared with each other using either equality or identity, as specified in the list constructor.
Use an enhanced 'for' loop to notify listeners. The recommended code sequence for notifying all registered listeners of say,
FooListener#eventHappened(Event)
, is:ListenerList<FooListener> fooListeners = new ListenerList<>(); //... for (FooListener listener : fooListeners) { listener.eventHappened(event); }
Legacy code may still call
getListeners()
and then use a 'for' loop to iterate theObject[]
. This might be insignificantly faster, but it lacks type-safety and risks inadvertent modifications to the array.This class can be used without OSGi running.
- Since:
- org.eclipse.equinox.common 3.2
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Constructor Summary
Constructors Constructor Description ListenerList()
Creates a listener list in which listeners are compared using equality.ListenerList(int mode)
Creates a listener list using the provided comparison mode.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
add(E listener)
Adds a listener to this list.void
clear()
Removes all listeners from this list.Object[]
getListeners()
Returns an array containing all the registered listeners.boolean
isEmpty()
Returns whether this listener list is empty.Iterator<E>
iterator()
Returns an iterator over all the registered listeners.Stream<E>
parallelStream()
Returns a parallelStream
over the registered listeners.void
remove(Object listener)
Removes a listener from this list.int
size()
Returns the number of registered listeners.Spliterator<E>
spliterator()
Returns a Spliterator covering the registered listeners.Stream<E>
stream()
Returns a sequentialStream
over the registered listeners.String
toString()
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Field Detail
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EQUALITY
public static final int EQUALITY
Mode constant (value 0) indicating that listeners should be considered the same if they are equal.- See Also:
- Constant Field Values
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IDENTITY
public static final int IDENTITY
Mode constant (value 1) indicating that listeners should be considered the same if they are identical.- See Also:
- Constant Field Values
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Constructor Detail
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ListenerList
public ListenerList()
Creates a listener list in which listeners are compared using equality.
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ListenerList
public ListenerList(int mode)
Creates a listener list using the provided comparison mode.- Parameters:
mode
- The mode used to determine if listeners are the same.
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Method Detail
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add
public void add(E listener)
Adds a listener to this list. This method has no effect if the same listener is already registered.- Parameters:
listener
- the non-null
listener to add
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getListeners
public Object[] getListeners()
Returns an array containing all the registered listeners. The resulting array is unaffected by subsequent adds or removes. If there are no listeners registered, the result is an empty array. Use this method when notifying listeners, so that any modifications to the listener list during the notification will have no effect on the notification itself.Note: Callers of this method must not modify the returned array.
Note: The recommended and type-safe way to iterate this list is to use an enhanced 'for' statement, see
ListenerList
. This method is deprecated for new code.- Returns:
- the list of registered listeners
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iterator
public Iterator<E> iterator()
Returns an iterator over all the registered listeners. The resulting iterator is unaffected by subsequent adds or removes. Use this method when notifying listeners, so that any modifications to the listener list during the notification will have no effect on the notification itself.
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isEmpty
public boolean isEmpty()
Returns whether this listener list is empty.- Returns:
true
if there are no registered listeners, andfalse
otherwise
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remove
public void remove(Object listener)
Removes a listener from this list. Has no effect if the same listener was not already registered.- Parameters:
listener
- the non-null
listener to remove
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size
public int size()
Returns the number of registered listeners.- Returns:
- the number of registered listeners
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clear
public void clear()
Removes all listeners from this list.
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spliterator
public Spliterator<E> spliterator()
Returns a Spliterator covering the registered listeners.The spliterator reports Spliterator.SIZED, Spliterator.SUBSIZED, Spliterator.ORDERED, and Spliterator.IMMUTABLE
- Specified by:
spliterator
in interfaceIterable<E>
- Returns:
- a spliterator for listeners
- Since:
- org.eclipse.equinox.common 3.9
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stream
public Stream<E> stream()
Returns a sequentialStream
over the registered listeners.- Returns:
- a sequential
Stream
over the registered listeners. - Since:
- org.eclipse.equinox.common 3.9
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parallelStream
public Stream<E> parallelStream()
Returns a parallelStream
over the registered listeners.- Returns:
- a parallel
Stream
over the registered listeners. - Since:
- org.eclipse.equinox.common 3.9
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