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package java.beans;

import java.util.ArrayList;
import java.util.Collections;
import java.util.EventListener;
import java.util.EventListenerProxy;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

This is an abstract class that provides base functionality for the PropertyChangeSupport class and the VetoableChangeSupport class. 
Author:
Sergey A. Malenkov
See Also:
PropertyChangeListenerMap
VetoableChangeListenerMap/**
 * This is an abstract class that provides base functionality
 * for the {@link PropertyChangeSupport PropertyChangeSupport} class
 * and the {@link VetoableChangeSupport VetoableChangeSupport} class.
 *
 * @see PropertyChangeListenerMap
 * @see VetoableChangeListenerMap
 *
 * @author Sergey A. Malenkov
 */
abstract class ChangeListenerMap<L extends EventListener> {
    private Map<String, L[]> map;

    
Creates an array of listeners. This method can be optimized by using the same instance of the empty array when length is equal to 0. 
Params:
length –  the array length
Returns:
       an array with specified length/**
     * Creates an array of listeners.
     * This method can be optimized by using
     * the same instance of the empty array
     * when {@code length} is equal to {@code 0}.
     *
     * @param length  the array length
     * @return        an array with specified length
     */
    protected abstract L[] newArray(int length);

    
Creates a proxy listener for the specified property.
Params:
name –      the name of the property to listen on
listener –  the listener to process events
Returns:
         a proxy listener/**
     * Creates a proxy listener for the specified property.
     *
     * @param name      the name of the property to listen on
     * @param listener  the listener to process events
     * @return          a proxy listener
     */
    protected abstract L newProxy(String name, L listener);

    
Adds a listener to the list of listeners for the specified property.
This listener is called as many times as it was added.
Params:
name –      the name of the property to listen on
listener –  the listener to process events/**
     * Adds a listener to the list of listeners for the specified property.
     * This listener is called as many times as it was added.
     *
     * @param name      the name of the property to listen on
     * @param listener  the listener to process events
     */
    public final synchronized void add(String name, L listener) {
        if (this.map == null) {
            this.map = new HashMap<>();
        }
        L[] array = this.map.get(name);
        int size = (array != null)
                ? array.length
                : 0;

        L[] clone = newArray(size + 1);
        clone[size] = listener;
        if (array != null) {
            System.arraycopy(array, 0, clone, 0, size);
        }
        this.map.put(name, clone);
    }

    
Removes a listener from the list of listeners for the specified property.
If the listener was added more than once to the same event source,
this listener will be notified one less time after being removed.
Params:
name –      the name of the property to listen on
listener –  the listener to process events/**
     * Removes a listener from the list of listeners for the specified property.
     * If the listener was added more than once to the same event source,
     * this listener will be notified one less time after being removed.
     *
     * @param name      the name of the property to listen on
     * @param listener  the listener to process events
     */
    public final synchronized void remove(String name, L listener) {
        if (this.map != null) {
            L[] array = this.map.get(name);
            if (array != null) {
                for (int i = 0; i < array.length; i++) {
                    if (listener.equals(array[i])) {
                        int size = array.length - 1;
                        if (size > 0) {
                            L[] clone = newArray(size);
                            System.arraycopy(array, 0, clone, 0, i);
                            System.arraycopy(array, i + 1, clone, i, size - i);
                            this.map.put(name, clone);
                        }
                        else {
                            this.map.remove(name);
                            if (this.map.isEmpty()) {
                                this.map = null;
                            }
                        }
                        break;
                    }
                }
            }
        }
    }

    
Returns the list of listeners for the specified property.
Params:
name –  the name of the property
Returns:
     the corresponding list of listeners/**
     * Returns the list of listeners for the specified property.
     *
     * @param name  the name of the property
     * @return      the corresponding list of listeners
     */
    public final synchronized L[] get(String name) {
        return (this.map != null)
                ? this.map.get(name)
                : null;
    }

    
Sets new list of listeners for the specified property.
Params:
name –       the name of the property
listeners –  new list of listeners/**
     * Sets new list of listeners for the specified property.
     *
     * @param name       the name of the property
     * @param listeners  new list of listeners
     */
    public final void set(String name, L[] listeners) {
        if (listeners != null) {
            if (this.map == null) {
                this.map = new HashMap<>();
            }
            this.map.put(name, listeners);
        }
        else if (this.map != null) {
            this.map.remove(name);
            if (this.map.isEmpty()) {
                this.map = null;
            }
        }
    }

    
Returns all listeners in the map.
Returns:
an array of all listeners/**
     * Returns all listeners in the map.
     *
     * @return an array of all listeners
     */
    public final synchronized L[] getListeners() {
        if (this.map == null) {
            return newArray(0);
        }
        List<L> list = new ArrayList<>();

        L[] listeners = this.map.get(null);
        if (listeners != null) {
            for (L listener : listeners) {
                list.add(listener);
            }
        }
        for (Entry<String, L[]> entry : this.map.entrySet()) {
            String name = entry.getKey();
            if (name != null) {
                for (L listener : entry.getValue()) {
                    list.add(newProxy(name, listener));
                }
            }
        }
        return list.toArray(newArray(list.size()));
    }

    
Returns listeners that have been associated with the named property.
Params:
name –  the name of the property
Returns:
an array of listeners for the named property/**
     * Returns listeners that have been associated with the named property.
     *
     * @param name  the name of the property
     * @return an array of listeners for the named property
     */
    public final L[] getListeners(String name) {
        if (name != null) {
            L[] listeners = get(name);
            if (listeners != null) {
                return listeners.clone();
            }
        }
        return newArray(0);
    }

    
Indicates whether the map contains
at least one listener to be notified.
Params:
name –  the name of the property
Returns:
 true if at least one listener exists or false otherwise/**
     * Indicates whether the map contains
     * at least one listener to be notified.
     *
     * @param name  the name of the property
     * @return      {@code true} if at least one listener exists or
     *              {@code false} otherwise
     */
    public final synchronized boolean hasListeners(String name) {
        if (this.map == null) {
            return false;
        }
        L[] array = this.map.get(null);
        return (array != null) || ((name != null) && (null != this.map.get(name)));
    }

    
Returns a set of entries from the map.
Each entry is a pair consisted of the property name
and the corresponding list of listeners.
Returns:
a set of entries from the map/**
     * Returns a set of entries from the map.
     * Each entry is a pair consisted of the property name
     * and the corresponding list of listeners.
     *
     * @return a set of entries from the map
     */
    public final Set<Entry<String, L[]>> getEntries() {
        return (this.map != null)
                ? this.map.entrySet()
                : Collections.<Entry<String, L[]>>emptySet();
    }

    
Extracts a real listener from the proxy listener.
It is necessary because default proxy class is not serializable.
Returns:
a real listener/**
     * Extracts a real listener from the proxy listener.
     * It is necessary because default proxy class is not serializable.
     *
     * @return a real listener
     */
    public abstract L extract(L listener);
}