Package EDU.oswego.cs.dl.util.concurrent
Class PropertyChangeMulticaster
- java.lang.Object
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- EDU.oswego.cs.dl.util.concurrent.PropertyChangeMulticaster
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- All Implemented Interfaces:
Serializable
public class PropertyChangeMulticaster extends Object implements Serializable
This class is interoperable with java.beans.PropertyChangeSupport, but relies on a streamlined copy-on-write scheme similar to that used in CopyOnWriteArrayList. This leads to much better performance in most event-intensive programs. It also adheres to clarified semantics of add and remove operations.Sample usage.
class Thing { protected Color myColor = Color.red; // an example property protected PropertyChangeMulticaster listeners = new PropertyChangeMulticaster(this); // registration methods, including: void addListener(PropertyChangeListener l) { // Use the `ifAbsent' version to avoid duplicate notifications listeners.addPropertyChangeListenerIfAbsent(l); } public synchronized Color getColor() { // accessor return myColor; } // internal synchronized state change method; returns old value protected synchronized Color assignColor(Color newColor) { Color oldColor = myColor; myColor = newColor; return oldColor; } public void setColor(Color newColor) { // atomically change state Color oldColor = assignColor(newColor); // broadcast change notification without holding synch lock listeners.firePropertyChange("color", oldColor, newColor); } }
- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description protected HashMap
children
HashMap for managing listeners for specific properties.protected PropertyChangeListener[]
listeners
The array of listeners.protected Object
source
The object to be provided as the "source" for any generated events.
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Constructor Summary
Constructors Constructor Description PropertyChangeMulticaster(Object sourceBean)
Constructs aPropertyChangeMulticaster
object.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
addPropertyChangeListener(PropertyChangeListener listener)
Add a VetoableChangeListener to the listener list.void
addPropertyChangeListener(String propertyName, PropertyChangeListener listener)
Add a PropertyChangeListener for a specific property.void
addPropertyChangeListenerIfAbsent(PropertyChangeListener listener)
Add a PropertyChangeListener to the listener list if it is not already present.void
addPropertyChangeListenerIfAbsent(String propertyName, PropertyChangeListener listener)
Add a PropertyChangeListener for a specific property, if it is not already registered.void
firePropertyChange(PropertyChangeEvent evt)
Fire an existing PropertyChangeEvent to any registered listeners.void
firePropertyChange(String propertyName, boolean oldValue, boolean newValue)
Report a boolean bound property update to any registered listeners.void
firePropertyChange(String propertyName, int oldValue, int newValue)
Report an int bound property update to any registered listeners.void
firePropertyChange(String propertyName, Object oldValue, Object newValue)
Report a bound property update to any registered listeners.protected PropertyChangeMulticaster
getChild(String propertyName)
Return the child associated with property, or null if no suchboolean
hasListeners(String propertyName)
Check if there are any listeners for a specific property.protected void
multicast(PropertyChangeEvent evt)
Helper method to relay evt to all listeners.void
removePropertyChangeListener(PropertyChangeListener listener)
Remove a PropertyChangeListener from the listener list.void
removePropertyChangeListener(String propertyName, PropertyChangeListener listener)
Remove a PropertyChangeListener for a specific property.
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Field Detail
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listeners
protected transient PropertyChangeListener[] listeners
The array of listeners. Copied on each update
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source
protected final Object source
The object to be provided as the "source" for any generated events.
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children
protected HashMap children
HashMap for managing listeners for specific properties. Maps property names to PropertyChangeMulticaster objects.
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Constructor Detail
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PropertyChangeMulticaster
public PropertyChangeMulticaster(Object sourceBean)
Constructs aPropertyChangeMulticaster
object.- Parameters:
sourceBean
- The bean to be given as the source for any events.- Throws:
NullPointerException
- if sourceBean is null
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Method Detail
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getChild
protected PropertyChangeMulticaster getChild(String propertyName)
Return the child associated with property, or null if no such
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addPropertyChangeListener
public void addPropertyChangeListener(PropertyChangeListener listener)
Add a VetoableChangeListener to the listener list. The listener is registered for all properties. If the listener is added multiple times, it will receive multiple change notifications upon any firePropertyChange- Parameters:
listener
- The PropertyChangeListener to be added- Throws:
NullPointerException
- If listener is null
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addPropertyChangeListenerIfAbsent
public void addPropertyChangeListenerIfAbsent(PropertyChangeListener listener)
Add a PropertyChangeListener to the listener list if it is not already present. The listener is registered for all properties. The operation maintains Set semantics: If the listener is already registered, the operation has no effect.- Parameters:
listener
- The PropertyChangeListener to be added- Throws:
NullPointerException
- If listener is null
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removePropertyChangeListener
public void removePropertyChangeListener(PropertyChangeListener listener)
Remove a PropertyChangeListener from the listener list. It removes at most one occurrence of the given listener. If the listener was added multiple times it must be removed mulitple times. This removes a PropertyChangeListener that was registered for all properties, and has no effect if registered for only one or more specified properties.- Parameters:
listener
- The PropertyChangeListener to be removed
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addPropertyChangeListener
public void addPropertyChangeListener(String propertyName, PropertyChangeListener listener)
Add a PropertyChangeListener for a specific property. The listener will be invoked only when a call on firePropertyChange names that specific property. However, if a listener is registered both for all properties and a specific property, it will receive multiple notifications upon changes to that property.- Parameters:
propertyName
- The name of the property to listen on.listener
- The PropertyChangeListener to be added- Throws:
NullPointerException
- If listener is null
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addPropertyChangeListenerIfAbsent
public void addPropertyChangeListenerIfAbsent(String propertyName, PropertyChangeListener listener)
Add a PropertyChangeListener for a specific property, if it is not already registered. The listener will be invoked only when a call on firePropertyChange names that specific property.- Parameters:
propertyName
- The name of the property to listen on.listener
- The PropertyChangeListener to be added- Throws:
NullPointerException
- If listener is null
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removePropertyChangeListener
public void removePropertyChangeListener(String propertyName, PropertyChangeListener listener)
Remove a PropertyChangeListener for a specific property. Affects only the given property. If the listener is also registered for all properties, then it will continue to be registered for them.- Parameters:
propertyName
- The name of the property that was listened on.listener
- The PropertyChangeListener to be removed
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multicast
protected void multicast(PropertyChangeEvent evt)
Helper method to relay evt to all listeners. Called by all public firePropertyChange methods.
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firePropertyChange
public void firePropertyChange(String propertyName, Object oldValue, Object newValue)
Report a bound property update to any registered listeners. No event is fired if old and new are equal and non-null.- Parameters:
propertyName
- The programmatic name of the property that was changed.oldValue
- The old value of the property.newValue
- The new value of the property.
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firePropertyChange
public void firePropertyChange(String propertyName, int oldValue, int newValue)
Report an int bound property update to any registered listeners. No event is fired if old and new are equal and non-null.This is merely a convenience wrapper around the more general firePropertyChange method that takes Object values.
- Parameters:
propertyName
- The programmatic name of the property that was changed.oldValue
- The old value of the property.newValue
- The new value of the property.
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firePropertyChange
public void firePropertyChange(String propertyName, boolean oldValue, boolean newValue)
Report a boolean bound property update to any registered listeners. No event is fired if old and new are equal and non-null.This is merely a convenience wrapper around the more general firePropertyChange method that takes Object values.
- Parameters:
propertyName
- The programmatic name of the property that was changed.oldValue
- The old value of the property.newValue
- The new value of the property.
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firePropertyChange
public void firePropertyChange(PropertyChangeEvent evt)
Fire an existing PropertyChangeEvent to any registered listeners. No event is fired if the given event's old and new values are equal and non-null.- Parameters:
evt
- The PropertyChangeEvent object.
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hasListeners
public boolean hasListeners(String propertyName)
Check if there are any listeners for a specific property. If propertyName is null, return whether there are any listeners at all.- Parameters:
propertyName
- the property name.- Returns:
- true if there are one or more listeners for the given property
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