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83 benjamin 1 
package org.tela_botanica.del.client.utils;
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import java.util.ArrayList;
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import java.util.List;
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public class GwtObservable {
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	List<GwtObserver> observers = new ArrayList<GwtObserver>();
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	boolean changed = false;
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	/**
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	 * Constructs a new {@code Observable} object.
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	 */
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	public GwtObservable() {
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		super();
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	}
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	/**
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	 * Adds the specified observer to the list of observers. If it is already
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	 * registered, it is not added a second time.
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	 *
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	 * @param observer
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	 *            the Observer to add.
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	 */
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	public void addObserver(GwtObserver observer) {
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		if (observer == null) {
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			throw new NullPointerException();
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		}
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		synchronized (this) {
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			if (!observers.contains(observer))
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				observers.add(observer);
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		}
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	}
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	/**
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	 * Clears the changed flag for this {@code Observable}. After calling
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	 * {@code clearChanged()}, {@code hasChanged()} will return {@code false}.
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	 */
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	protected void clearChanged() {
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		changed = false;
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	}
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	/**
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	 * Returns the number of observers registered to this {@code Observable}.
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	 *
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	 * @return the number of observers.
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	 */
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	public int countObservers() {
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		return observers.size();
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	}
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	/**
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	 * Removes the specified observer from the list of observers. Passing null
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	 * won't do anything.
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	 *
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	 * @param observer
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	 *            the observer to remove.
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	 */
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	public synchronized void deleteObserver(GwtObserver observer) {
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		observers.remove(observer);
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	}
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	/**
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	 * Removes all observers from the list of observers.
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	 */
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	public synchronized void deleteObservers() {
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		observers.clear();
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	}
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	/**
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	 * Returns the changed flag for this {@code Observable}.
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	 *
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	 * @return {@code true} when the changed flag for this {@code Observable} is
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	 *         set, {@code false} otherwise.
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	 */
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	public boolean hasChanged() {
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		return changed;
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	}
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	/**
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	 * If {@code hasChanged()} returns {@code true}, calls the {@code update()}
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	 * method for every observer in the list of observers using null as the
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	 * argument. Afterwards, calls {@code clearChanged()}.
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	 * <p>
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	 * Equivalent to calling {@code notifyObservers(null)}.
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	 */
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	public void notifyObservers() {
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		notifyObservers(null);
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	}
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	/**
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	 * If {@code hasChanged()} returns {@code true}, calls the {@code update()}
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	 * method for every Observer in the list of observers using the specified
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	 * argument. Afterwards calls {@code clearChanged()}.
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	 *
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	 * @param data
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	 *            the argument passed to {@code update()}.
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	 */
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	public void notifyObservers(Object data) {
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		int size = 0;
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		GwtObserver[] arrays = null;
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		synchronized (this) {
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			if (hasChanged()) {
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				clearChanged();
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				size = observers.size();
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				arrays = new GwtObserver[size];
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				observers.toArray(arrays);
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			}
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		}
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		if (arrays != null) {
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			for (GwtObserver observer : arrays) {
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				observer.update(this, data);
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			}
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		}
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	}
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	/**
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	 * Sets the changed flag for this {@code Observable}. After calling
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	 * {@code setChanged()}, {@code hasChanged()} will return {@code true}.
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	 */
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	protected void setChanged() {
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		changed = true;
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	}
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}