Observer
Stay organized with collections
Save and categorize content based on your preferences.
A class can implement the Observer interface when it
wants to be informed of changes in observable objects.
Public Methods
public
abstract
void
update
(Observable o, Object arg)
This method is called whenever the observed object is changed. An
application calls an Observable object's
notifyObservers method to have all the object's
observers notified of the change.
Parameters
| o |
the observable object. |
| arg |
an argument passed to the notifyObservers
method.
|
Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2024-07-10 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2024-07-10 UTC."],[[["\u003cp\u003eThe \u003ccode\u003eObserver\u003c/code\u003e interface allows a class to be informed about changes in observable objects.\u003c/p\u003e\n"],["\u003cp\u003eImplementing the \u003ccode\u003eObserver\u003c/code\u003e interface requires the class to define the \u003ccode\u003eupdate\u003c/code\u003e method, which is called when the observed object changes.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003eupdate\u003c/code\u003e method receives the changed \u003ccode\u003eObservable\u003c/code\u003e object and an optional argument passed from the \u003ccode\u003enotifyObservers\u003c/code\u003e method.\u003c/p\u003e\n"]]],[],null,["# Observer\n\npublic interface **Observer** \nA class can implement the `Observer` interface when it\nwants to be informed of changes in observable objects. \n\n##### See Also\n\n- [Observable](../../../reference/java/util/Observable.html) \n\n### Public Method Summary\n\n|---------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| abstract void | [update](../../../reference/java/util/Observer.html#update(java.util.Observable,%20java.lang.Object))([Observable](../../../reference/java/util/Observable.html) o, [Object](../../../reference/java/lang/Object.html) arg) This method is called whenever the observed object is changed. |\n\nPublic Methods\n--------------\n\n#### public abstract void\n**update**\n([Observable](../../../reference/java/util/Observable.html) o, [Object](../../../reference/java/lang/Object.html) arg)\n\nThis method is called whenever the observed object is changed. An\napplication calls an Observable object's\n`notifyObservers` method to have all the object's\nobservers notified of the change. \n\n##### Parameters\n\n| o | the observable object. |\n| arg | an argument passed to the `notifyObservers` method. |\n|-----|-----------------------------------------------------|"]]
