My first initial commit with all of mine experimental changes.

Dmitry Kabak (userdima committed 13 years ago

Commit d37b88d1 parent 3f5b46618352 files · +2598093 −-8690Browse files

Showing the changes to java/pkg/java/util/Observable.java (1 of 18352 files). Show all

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	1	+/*
	2	+ * Copyright (c) 1994, 2004, Oracle and/or its affiliates. All rights reserved.
	3	+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	4	+ *
	5	+ * This code is free software; you can redistribute it and/or modify it
	6	+ * under the terms of the GNU General Public License version 2 only, as
	7	+ * published by the Free Software Foundation. Oracle designates this
	8	+ * particular file as subject to the "Classpath" exception as provided
	9	+ * by Oracle in the LICENSE file that accompanied this code.
	10	+ *
	11	+ * This code is distributed in the hope that it will be useful, but WITHOUT
	12	+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	13	+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	14	+ * version 2 for more details (a copy is included in the LICENSE file that
	15	+ * accompanied this code).
	16	+ *
	17	+ * You should have received a copy of the GNU General Public License version
	18	+ * 2 along with this work; if not, write to the Free Software Foundation,
	19	+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	20	+ *
	21	+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	22	+ * or visit www.oracle.com if you need additional information or have any
	23	+ * questions.
	24	+ */
	25	+
	26	+package java.util;
	27	+
	28	+/**
	29	+ * This class represents an observable object, or "data"
	30	+ * in the model-view paradigm. It can be subclassed to represent an
	31	+ * object that the application wants to have observed.
	32	+ * <p>
	33	+ * An observable object can have one or more observers. An observer
	34	+ * may be any object that implements interface <tt>Observer</tt>. After an
	35	+ * observable instance changes, an application calling the
	36	+ * <code>Observable</code>'s <code>notifyObservers</code> method
	37	+ * causes all of its observers to be notified of the change by a call
	38	+ * to their <code>update</code> method.
	39	+ * <p>
	40	+ * The order in which notifications will be delivered is unspecified.
	41	+ * The default implementation provided in the Observable class will
	42	+ * notify Observers in the order in which they registered interest, but
	43	+ * subclasses may change this order, use no guaranteed order, deliver
	44	+ * notifications on separate threads, or may guarantee that their
	45	+ * subclass follows this order, as they choose.
	46	+ * <p>
	47	+ * Note that this notification mechanism is has nothing to do with threads
	48	+ * and is completely separate from the <tt>wait</tt> and <tt>notify</tt>
	49	+ * mechanism of class <tt>Object</tt>.
	50	+ * <p>
	51	+ * When an observable object is newly created, its set of observers is
	52	+ * empty. Two observers are considered the same if and only if the
	53	+ * <tt>equals</tt> method returns true for them.
	54	+ *
	55	+ * @author Chris Warth
	56	+ * @see java.util.Observable#notifyObservers()
	57	+ * @see java.util.Observable#notifyObservers(java.lang.Object)
	58	+ * @see java.util.Observer
	59	+ * @see java.util.Observer#update(java.util.Observable, java.lang.Object)
	60	+ * @since JDK1.0
	61	+ */
	62	+public class Observable {
	63	+ private boolean changed = false;
	64	+ private Vector obs;
	65	+
	66	+ /** Construct an Observable with zero Observers. */
	67	+
	68	+ public Observable() {
	69	+ obs = new Vector();
	70	+ }
	71	+
	72	+ /**
	73	+ * Adds an observer to the set of observers for this object, provided
	74	+ * that it is not the same as some observer already in the set.
	75	+ * The order in which notifications will be delivered to multiple
	76	+ * observers is not specified. See the class comment.
	77	+ *
	78	+ * @param o an observer to be added.
	79	+ * @throws NullPointerException if the parameter o is null.
	80	+ */
	81	+ public synchronized void addObserver(Observer o) {
	82	+ if (o == null)
	83	+ throw new NullPointerException();
	84	+ if (!obs.contains(o)) {
	85	+ obs.addElement(o);
	86	+ }
	87	+ }
	88	+
	89	+ /**
	90	+ * Deletes an observer from the set of observers of this object.
	91	+ * Passing <CODE>null</CODE> to this method will have no effect.
	92	+ * @param o the observer to be deleted.
	93	+ */
	94	+ public synchronized void deleteObserver(Observer o) {
	95	+ obs.removeElement(o);
	96	+ }
	97	+
	98	+ /**
	99	+ * If this object has changed, as indicated by the
	100	+ * <code>hasChanged</code> method, then notify all of its observers
	101	+ * and then call the <code>clearChanged</code> method to
	102	+ * indicate that this object has no longer changed.
	103	+ * <p>
	104	+ * Each observer has its <code>update</code> method called with two
	105	+ * arguments: this observable object and <code>null</code>. In other
	106	+ * words, this method is equivalent to:
	107	+ * <blockquote><tt>
	108	+ * notifyObservers(null)</tt></blockquote>
	109	+ *
	110	+ * @see java.util.Observable#clearChanged()
	111	+ * @see java.util.Observable#hasChanged()
	112	+ * @see java.util.Observer#update(java.util.Observable, java.lang.Object)
	113	+ */
	114	+ public void notifyObservers() {
	115	+ notifyObservers(null);
	116	+ }
	117	+
	118	+ /**
	119	+ * If this object has changed, as indicated by the
	120	+ * <code>hasChanged</code> method, then notify all of its observers
	121	+ * and then call the <code>clearChanged</code> method to indicate
	122	+ * that this object has no longer changed.
	123	+ * <p>
	124	+ * Each observer has its <code>update</code> method called with two
	125	+ * arguments: this observable object and the <code>arg</code> argument.
	126	+ *
	127	+ * @param arg any object.
	128	+ * @see java.util.Observable#clearChanged()
	129	+ * @see java.util.Observable#hasChanged()
	130	+ * @see java.util.Observer#update(java.util.Observable, java.lang.Object)
	131	+ */
	132	+ public void notifyObservers(Object arg) {
	133	+ /*
	134	+ * a temporary array buffer, used as a snapshot of the state of
	135	+ * current Observers.
	136	+ */
	137	+ Object[] arrLocal;
	138	+
	139	+ synchronized (this) {
	140	+ /* We don't want the Observer doing callbacks into
	141	+ * arbitrary code while holding its own Monitor.
	142	+ * The code where we extract each Observable from
	143	+ * the Vector and store the state of the Observer
	144	+ * needs synchronization, but notifying observers
	145	+ * does not (should not). The worst result of any
	146	+ * potential race-condition here is that:
	147	+ * 1) a newly-added Observer will miss a
	148	+ * notification in progress
	149	+ * 2) a recently unregistered Observer will be
	150	+ * wrongly notified when it doesn't care
	151	+ */
	152	+ if (!changed)
	153	+ return;
	154	+ arrLocal = obs.toArray();
	155	+ clearChanged();
	156	+ }
	157	+
	158	+ for (int i = arrLocal.length-1; i>=0; i--)
	159	+ ((Observer)arrLocal[i]).update(this, arg);
	160	+ }
	161	+
	162	+ /**
	163	+ * Clears the observer list so that this object no longer has any observers.
	164	+ */
	165	+ public synchronized void deleteObservers() {
	166	+ obs.removeAllElements();
	167	+ }
	168	+
	169	+ /**
	170	+ * Marks this <tt>Observable</tt> object as having been changed; the
	171	+ * <tt>hasChanged</tt> method will now return <tt>true</tt>.
	172	+ */
	173	+ protected synchronized void setChanged() {
	174	+ changed = true;
	175	+ }
	176	+
	177	+ /**
	178	+ * Indicates that this object has no longer changed, or that it has
	179	+ * already notified all of its observers of its most recent change,
	180	+ * so that the <tt>hasChanged</tt> method will now return <tt>false</tt>.
	181	+ * This method is called automatically by the
	182	+ * <code>notifyObservers</code> methods.
	183	+ *
	184	+ * @see java.util.Observable#notifyObservers()
	185	+ * @see java.util.Observable#notifyObservers(java.lang.Object)
	186	+ */
	187	+ protected synchronized void clearChanged() {
	188	+ changed = false;
	189	+ }
	190	+
	191	+ /**
	192	+ * Tests if this object has changed.
	193	+ *
	194	+ * @return <code>true</code> if and only if the <code>setChanged</code>
	195	+ * method has been called more recently than the
	196	+ * <code>clearChanged</code> method on this object;
	197	+ * <code>false</code> otherwise.
	198	+ * @see java.util.Observable#clearChanged()
	199	+ * @see java.util.Observable#setChanged()
	200	+ */
	201	+ public synchronized boolean hasChanged() {
	202	+ return changed;
	203	+ }
	204	+
	205	+ /**
	206	+ * Returns the number of observers of this <tt>Observable</tt> object.
	207	+ *
	208	+ * @return the number of observers of this object.
	209	+ */
	210	+ public synchronized int countObservers() {
	211	+ return obs.size();
	212	+ }
	213	+}