Java.util.Observable.deleteObservers() Java.util.Observable.deleteObserver() Java.util.Observable.hasChanged() 描述 该java.util.Observable.deleteObservers()方法清除观察者列表。此对象将不再具有任何观察者。 声明 以下是java.util.Observable.deleteObservers()方法的声明 public void deleteObservers() 参数 NA 返回值 NA 异常 NA 实例 以下示例显示了java.util.Observable.deleteObservers()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 String name; public ObservableDemo(String name) { this.name = name; } public static void main(String[] args) { // create watched and watcher objects ObservedObject watched = new ObservedObject("Original Value"); // watcher object listens to object change ObservableDemo watcher1 = new ObservableDemo("Watcher1"); ObservableDemo watcher2 = new ObservableDemo("Watcher2"); // trigger value change watched.setValue("Value before addObserver"); // add observer to the watched object watched.addObserver(watcher1); watched.addObserver(watcher2); // trigger value change watched.setValue("Value after addObserver"); // delete all observers watched.deleteObservers(); // trigger value change watched.setValue("Value after deleteObservers"); } public void update(Observable obj, Object arg) { System.out.println(name+" 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 Watcher2 called with Arguments: Value after addObserver Watcher1 called with Arguments: Value after addObserver Value changed to new value: Value after deleteObservers Java.util.Observable.deleteObserver() Java.util.Observable.hasChanged()