Java.util.Observable.deleteObserver() Java.util.Observable.countObservers() Java.util.Observable.deleteObservers() 描述 所述java.util.Observable.deleteObserver(Observer O)方法删除指定观察者ø从所述一组对象的观察者的。 声明 以下是java.util.Observable.deleteObserver()方法的声明 public void deleteObserver(Observer o) 参数 o - 从观察员集中删除的观察者。 返回值 NA 异常 NA 实例 以下示例显示了java.util.Observable.deleteObserver(Observer)方法的用法。 package com.tutorialspoint; import java.util.Observable; import java.util.Observer; class ObservedObject extends Observable { private String watchedValue; public ObservedObject(String value) { watchedValue = value; } public void setValue(String value) { // if value has changed notify observers if(!watchedValue.equals(value)) { System.out.println("Value changed to new value: "+value); watchedValue = value; // mark as value changed setChanged(); // trigger notification notifyObservers(value); } } } public class ObservableDemo implements Observer { public static void main(String[] args) { // create watched and watcher objects ObservedObject watched = new ObservedObject("Original Value"); // watcher object listens to object change ObservableDemo watcher = new ObservableDemo(); // trigger value change watched.setValue("Value before addObserver"); // add observer to the watched object watched.addObserver(watcher); // trigger value change watched.setValue("Value after addObserver"); // delete observer watched.deleteObserver(watcher); // trigger value change watched.setValue("Value after deleteObserver"); } public void update(Observable obj, Object arg) { System.out.println("Update called with Arguments: "+arg); } } 让我们编译并运行上面的程序,这将产生以下结果 Value changed to new value: Value before addObserver Value changed to new value: Value after addObserver Update called with Arguments: Value after addObserver Value changed to new value: Value after deleteObserver Java.util.Observable.countObservers() Java.util.Observable.deleteObservers()