Subversion Repositories eFlore/Applications.del

package org.tela_botanica.del.client.utils;

import java.util.ArrayList;
import java.util.List;

public class GwtObservable {
        List<GwtObserver> observers = new ArrayList<GwtObserver>();

        boolean changed = false;

        /**
         * Constructs a new {@code Observable} object.
         */
        public GwtObservable() {
                super();
        }

        /**
         * Adds the specified observer to the list of observers. If it is already
         * registered, it is not added a second time.
         * 
         * @param observer
         *            the Observer to add.
         */
        public void addObserver(GwtObserver observer) {
                if (observer == null) {
                        throw new NullPointerException();
                }
                synchronized (this) {
                        if (!observers.contains(observer))
                                observers.add(observer);
                }
        }

        /**
         * Clears the changed flag for this {@code Observable}. After calling
         * {@code clearChanged()}, {@code hasChanged()} will return {@code false}.
         */
        protected void clearChanged() {
                changed = false;
        }

        /**
         * Returns the number of observers registered to this {@code Observable}.
         * 
         * @return the number of observers.
         */
        public int countObservers() {
                return observers.size();
        }

        /**
         * Removes the specified observer from the list of observers. Passing null
         * won't do anything.
         * 
         * @param observer
         *            the observer to remove.
         */
        public synchronized void deleteObserver(GwtObserver observer) {
                observers.remove(observer);
        }

        /**
         * Removes all observers from the list of observers.
         */
        public synchronized void deleteObservers() {
                observers.clear();
        }

        /**
         * Returns the changed flag for this {@code Observable}.
         * 
         * @return {@code true} when the changed flag for this {@code Observable} is
         *         set, {@code false} otherwise.
         */
        public boolean hasChanged() {
                return changed;
        }

        /**
         * If {@code hasChanged()} returns {@code true}, calls the {@code update()}
         * method for every observer in the list of observers using null as the
         * argument. Afterwards, calls {@code clearChanged()}.
         * <p>
         * Equivalent to calling {@code notifyObservers(null)}.
         */
        public void notifyObservers() {
                notifyObservers(null);
        }

        /**
         * If {@code hasChanged()} returns {@code true}, calls the {@code update()}
         * method for every Observer in the list of observers using the specified
         * argument. Afterwards calls {@code clearChanged()}.
         * 
         * @param data
         *            the argument passed to {@code update()}.
         */
        public void notifyObservers(Object data) {
                int size = 0;
                GwtObserver[] arrays = null;
                synchronized (this) {
                        if (hasChanged()) {
                                clearChanged();
                                size = observers.size();
                                arrays = new GwtObserver[size];
                                observers.toArray(arrays);
                        }
                }
                if (arrays != null) {
                        for (GwtObserver observer : arrays) {
                                observer.update(this, data);
                        }
                }
        }

        /**
         * Sets the changed flag for this {@code Observable}. After calling
         * {@code setChanged()}, {@code hasChanged()} will return {@code true}.
         */
        protected void setChanged() {
                changed = true;
        }

}