observable

可观察的类countObservers()方法 (Observable Class countObservers() method)

• countObservers() method is available in java.util package.

  countObservers()方法在java.util包中可用。

• countObservers() method is used to count the number of observers exists in this Observable.

  countObservers()方法用于计算此Observable中存在的观察者的数量。

• countObservers() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.

  countObservers()方法是一个非静态方法，只能通过类对象访问，如果尝试使用类名访问该方法，则会收到错误消息。

• countObservers() method does not throw an exception at the time of counting the observer.

  在计数观察者时， countObservers()方法不会引发异常。

Syntax:

句法：

public int countObservers();

Parameter(s):

参数：

• It does not accept any parameter.

  它不接受任何参数。

Return value:

返回值：

The return type of the method is int, it gets the number of observers in this Observable.

方法的返回类型为int ，它获取此Observable中的观察者数量。

Example:

例：

// Java program to demonstrate the example // of int countObservers() method of Observableimport java.util.*;// Implement Observers class class Observers_1 implements Observer {
       public void update(Observable obj, Object ob) {
           System.out.println("Obs1: ");    }}class Observers_2 implements Observer {
       public void update(Observable obj, Object ob) {
           System.out.println("Obs2: ");    }}// Implement Observed Classclass Observed extends Observable {
       // Function call    void countObs() {
           setChanged();        // By using notifyObservers() method is         // to notify all the observers that are        // implemented        notifyObservers();    }}public class CountObservers {
       // Implement Main Method    public static void main(String args[]) {
           Observed observed = new Observed();        Observers_1 obs1 = new Observers_1();        Observers_2 obs2 = new Observers_2();        observed.addObserver(obs1);        observed.addObserver(obs2);        // By using countObservers() method is        // to return the number of observers         // in this object        int count_obs = observed.countObservers();        System.out.println("observed.countObservers(): " + count_obs);        observed.countObs();    }}

Output

输出量

observed.countObservers(): 2Obs2: Obs1:

翻译自:

observable