Module java.base
Package java.util

Class Observable

  • @Deprecated(since="9")public classObservableextendsObject
    Deprecated.
    This class and theObserver interface have been deprecated. The event model supported byObserver andObservable is quite limited, the order of notifications delivered byObservable is unspecified, and state changes are not in one-for-one correspondence with notifications. For a richer event model, consider using thejava.beans package. For reliable and ordered messaging among threads, consider using one of the concurrent data structures in thejava.util.concurrent package. For reactive streams style programming, see theFlow API.
    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.

    An observable object can have one or more observers. An observer may be any object that implements interfaceObserver. After an observable instance changes, an application calling theObservable'snotifyObservers method causes all of its observers to be notified of the change by a call to theirupdate method.

    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.

    Note that this notification mechanism has nothing to do with threads and is completely separate from thewait andnotify mechanism of classObject.

    When an observable object is newly created, its set of observers is empty. Two observers are considered the same if and only if theequals method returns true for them.

    Since:
    1.0
    See Also:
    notifyObservers(),notifyObservers(java.lang.Object),Observer,Observer.update(java.util.Observable, java.lang.Object)

    • Constructor Summary

      Constructors 
      ConstructorDescription
      Observable()
      Deprecated.
      Construct an Observable with zero Observers.

    • Method Summary

      All Methods Instance Methods Concrete Methods Deprecated Methods 
      Modifier and TypeMethodDescription
      voidaddObserver​(Observer o)
      Deprecated.
      Adds an observer to the set of observers for this object, provided that it is not the same as some observer already in the set.
      protected voidclearChanged()
      Deprecated.
      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 thehasChanged method will now returnfalse.
      intcountObservers()
      Deprecated.
      Returns the number of observers of thisObservable object.
      voiddeleteObserver​(Observer o)
      Deprecated.
      Deletes an observer from the set of observers of this object.
      voiddeleteObservers()
      Deprecated.
      Clears the observer list so that this object no longer has any observers.
      booleanhasChanged()
      Deprecated.
      Tests if this object has changed.
      voidnotifyObservers()
      Deprecated.
      If this object has changed, as indicated by thehasChanged method, then notify all of its observers and then call theclearChanged method to indicate that this object has no longer changed.
      voidnotifyObservers​(Object arg)
      Deprecated.
      If this object has changed, as indicated by thehasChanged method, then notify all of its observers and then call theclearChanged method to indicate that this object has no longer changed.
      protected voidsetChanged()
      Deprecated.
      Marks thisObservable object as having been changed; thehasChanged method will now returntrue.

    • Constructor Detail

      • Observable

        public Observable()
        Deprecated.
        Construct an Observable with zero Observers.

    • Method Detail

      • addObserver

        public void addObserver​(Observer o)
        Deprecated.
        Adds an observer to the set of observers for this object, provided that it is not the same as some observer already in the set. The order in which notifications will be delivered to multiple observers is not specified. See the class comment.
        Parameters:
        o - an observer to be added.
        Throws:
        NullPointerException - if the parameter o is null.

      • deleteObserver

        public void deleteObserver​(Observer o)
        Deprecated.
        Deletes an observer from the set of observers of this object. Passingnull to this method will have no effect.
        Parameters:
        o - the observer to be deleted.

      • notifyObservers

        public void notifyObservers()
        Deprecated.
        If this object has changed, as indicated by thehasChanged method, then notify all of its observers and then call theclearChanged method to indicate that this object has no longer changed.

        Each observer has itsupdate method called with two arguments: this observable object andnull. In other words, this method is equivalent to:

        notifyObservers(null)

        See Also:
        clearChanged(),hasChanged(),Observer.update(java.util.Observable, java.lang.Object)

      • notifyObservers

        public void notifyObservers​(Object arg)
        Deprecated.
        If this object has changed, as indicated by thehasChanged method, then notify all of its observers and then call theclearChanged method to indicate that this object has no longer changed.

        Each observer has itsupdate method called with two arguments: this observable object and thearg argument.

        Parameters:
        arg - any object.
        See Also:
        clearChanged(),hasChanged(),Observer.update(java.util.Observable, java.lang.Object)

      • deleteObservers

        public void deleteObservers()
        Deprecated.
        Clears the observer list so that this object no longer has any observers.

      • setChanged

        protected void setChanged()
        Deprecated.
        Marks thisObservable object as having been changed; thehasChanged method will now returntrue.

      • clearChanged

        protected void clearChanged()
        Deprecated.
        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 thehasChanged method will now returnfalse. This method is called automatically by thenotifyObservers methods.
        See Also:
        notifyObservers(),notifyObservers(java.lang.Object)

      • hasChanged

        public boolean hasChanged()
        Deprecated.
        Tests if this object has changed.
        Returns:
        true if and only if thesetChanged method has been called more recently than theclearChanged method on this object;false otherwise.
        See Also:
        clearChanged(),setChanged()

      • countObservers

        public int countObservers()
        Deprecated.
        Returns the number of observers of thisObservable object.
        Returns:
        the number of observers of this object.