< prev index next >
src/java.base/share/classes/java/util/Observable.java
Print this page
*** 29,58 ****
* This class represents an observable object, or "data"
* in the model-view paradigm. It can be subclassed to represent an
* object that the application wants to have observed.
* <p>
* An observable object can have one or more observers. An observer
! * may be any object that implements interface <tt>Observer</tt>. After an
* observable instance changes, an application calling the
! * <code>Observable</code>'s <code>notifyObservers</code> method
* causes all of its observers to be notified of the change by a call
! * to their <code>update</code> method.
* <p>
* The order in which notifications will be delivered is unspecified.
* The default implementation provided in the Observable class will
* notify Observers in the order in which they registered interest, but
* subclasses may change this order, use no guaranteed order, deliver
* notifications on separate threads, or may guarantee that their
* subclass follows this order, as they choose.
* <p>
* Note that this notification mechanism has nothing to do with threads
! * and is completely separate from the <tt>wait</tt> and <tt>notify</tt>
! * mechanism of class <tt>Object</tt>.
* <p>
* When an observable object is newly created, its set of observers is
* empty. Two observers are considered the same if and only if the
! * <tt>equals</tt> method returns true for them.
*
* @author Chris Warth
* @see java.util.Observable#notifyObservers()
* @see java.util.Observable#notifyObservers(java.lang.Object)
* @see java.util.Observer
--- 29,58 ----
* This class represents an observable object, or "data"
* in the model-view paradigm. It can be subclassed to represent an
* object that the application wants to have observed.
* <p>
* An observable object can have one or more observers. An observer
! * may be any object that implements interface {@code Observer}. After an
* observable instance changes, an application calling the
! * {@code Observable}'s {@code notifyObservers} method
* causes all of its observers to be notified of the change by a call
! * to their {@code update} method.
* <p>
* The order in which notifications will be delivered is unspecified.
* The default implementation provided in the Observable class will
* notify Observers in the order in which they registered interest, but
* subclasses may change this order, use no guaranteed order, deliver
* notifications on separate threads, or may guarantee that their
* subclass follows this order, as they choose.
* <p>
* Note that this notification mechanism has nothing to do with threads
! * and is completely separate from the {@code wait} and {@code notify}
! * mechanism of class {@code Object}.
* <p>
* When an observable object is newly created, its set of observers is
* empty. Two observers are considered the same if and only if the
! * {@code equals} method returns true for them.
*
* @author Chris Warth
* @see java.util.Observable#notifyObservers()
* @see java.util.Observable#notifyObservers(java.lang.Object)
* @see java.util.Observer
*** 86,113 ****
}
}
/**
* Deletes an observer from the set of observers of this object.
! * Passing <CODE>null</CODE> to this method will have no effect.
* @param o the observer to be deleted.
*/
public synchronized void deleteObserver(Observer o) {
obs.removeElement(o);
}
/**
* If this object has changed, as indicated by the
! * <code>hasChanged</code> method, then notify all of its observers
! * and then call the <code>clearChanged</code> method to
* indicate that this object has no longer changed.
* <p>
! * Each observer has its <code>update</code> method called with two
! * arguments: this observable object and <code>null</code>. In other
* words, this method is equivalent to:
! * <blockquote><tt>
! * notifyObservers(null)</tt></blockquote>
*
* @see java.util.Observable#clearChanged()
* @see java.util.Observable#hasChanged()
* @see java.util.Observer#update(java.util.Observable, java.lang.Object)
*/
--- 86,113 ----
}
}
/**
* Deletes an observer from the set of observers of this object.
! * Passing {@code null} to this method will have no effect.
* @param o the observer to be deleted.
*/
public synchronized void deleteObserver(Observer o) {
obs.removeElement(o);
}
/**
* If this object has changed, as indicated by the
! * {@code hasChanged} method, then notify all of its observers
! * and then call the {@code clearChanged} method to
* indicate that this object has no longer changed.
* <p>
! * Each observer has its {@code update} method called with two
! * arguments: this observable object and {@code null}. In other
* words, this method is equivalent to:
! * <blockquote>{@code
! * notifyObservers(null)}</blockquote>
*
* @see java.util.Observable#clearChanged()
* @see java.util.Observable#hasChanged()
* @see java.util.Observer#update(java.util.Observable, java.lang.Object)
*/
*** 115,130 ****
notifyObservers(null);
}
/**
* If this object has changed, as indicated by the
! * <code>hasChanged</code> method, then notify all of its observers
! * and then call the <code>clearChanged</code> method to indicate
* that this object has no longer changed.
* <p>
! * Each observer has its <code>update</code> method called with two
! * arguments: this observable object and the <code>arg</code> argument.
*
* @param arg any object.
* @see java.util.Observable#clearChanged()
* @see java.util.Observable#hasChanged()
* @see java.util.Observer#update(java.util.Observable, java.lang.Object)
--- 115,130 ----
notifyObservers(null);
}
/**
* If this object has changed, as indicated by the
! * {@code hasChanged} method, then notify all of its observers
! * and then call the {@code clearChanged} method to indicate
* that this object has no longer changed.
* <p>
! * Each observer has its {@code update} method called with two
! * arguments: this observable object and the {@code arg} argument.
*
* @param arg any object.
* @see java.util.Observable#clearChanged()
* @see java.util.Observable#hasChanged()
* @see java.util.Observer#update(java.util.Observable, java.lang.Object)
*** 165,187 ****
public synchronized void deleteObservers() {
obs.removeAllElements();
}
/**
! * Marks this <tt>Observable</tt> object as having been changed; the
! * <tt>hasChanged</tt> method will now return <tt>true</tt>.
*/
protected synchronized void setChanged() {
changed = true;
}
/**
* Indicates that this object has no longer changed, or that it has
* already notified all of its observers of its most recent change,
! * so that the <tt>hasChanged</tt> method will now return <tt>false</tt>.
* This method is called automatically by the
! * <code>notifyObservers</code> methods.
*
* @see java.util.Observable#notifyObservers()
* @see java.util.Observable#notifyObservers(java.lang.Object)
*/
protected synchronized void clearChanged() {
--- 165,187 ----
public synchronized void deleteObservers() {
obs.removeAllElements();
}
/**
! * Marks this {@code Observable} object as having been changed; the
! * {@code hasChanged} method will now return {@code true}.
*/
protected synchronized void setChanged() {
changed = true;
}
/**
* Indicates that this object has no longer changed, or that it has
* already notified all of its observers of its most recent change,
! * so that the {@code hasChanged} method will now return {@code false}.
* This method is called automatically by the
! * {@code notifyObservers} methods.
*
* @see java.util.Observable#notifyObservers()
* @see java.util.Observable#notifyObservers(java.lang.Object)
*/
protected synchronized void clearChanged() {
*** 189,211 ****
}
/**
* Tests if this object has changed.
*
! * @return <code>true</code> if and only if the <code>setChanged</code>
* method has been called more recently than the
! * <code>clearChanged</code> method on this object;
! * <code>false</code> otherwise.
* @see java.util.Observable#clearChanged()
* @see java.util.Observable#setChanged()
*/
public synchronized boolean hasChanged() {
return changed;
}
/**
! * Returns the number of observers of this <tt>Observable</tt> object.
*
* @return the number of observers of this object.
*/
public synchronized int countObservers() {
return obs.size();
--- 189,211 ----
}
/**
* Tests if this object has changed.
*
! * @return {@code true} if and only if the {@code setChanged}
* method has been called more recently than the
! * {@code clearChanged} method on this object;
! * {@code false} otherwise.
* @see java.util.Observable#clearChanged()
* @see java.util.Observable#setChanged()
*/
public synchronized boolean hasChanged() {
return changed;
}
/**
! * Returns the number of observers of this {@code Observable} object.
*
* @return the number of observers of this object.
*/
public synchronized int countObservers() {
return obs.size();
< prev index next >