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  • Java 观察者模式

    定义:定义了对象之间的一对多依赖,让多个观察者对象同时监听某一个主题对象,当主题对象发生变化时,它的依赖者(观察者)都会收到通知并更新

    适用场景:

    关联行为场景,建立一套触发机制

    优点:

    1.观察者和被观察者之间建立一个抽象的耦合

    2.观察者模式支持广播通讯

    缺点:

    观察者之间有过多的细节依赖,提高时间消耗及程序复杂度

    使用得当,要避免循环调用

    import java.util.Observable;
    
    public class Course extends Observable {
        private  String courseName;
    
        public Course(String courseName) {
            this.courseName = courseName;
        }
    
        public String getCourseName() {
            return courseName;
        }
        public void produceQuestion(Course course,Question question){
            System.out.println(question.getUserName()+"在"+course.courseName+"提交了问题");
            setChanged();
            notifyObservers(question);
        }
    }
    

      

    public class Question {
        private String userName;
        private String questionContent;
    
        public String getUserName() {
            return userName;
        }
    
        public void setUserName(String userName) {
            this.userName = userName;
        }
    
        public String getQuestionContent() {
            return questionContent;
        }
    
        public void setQuestionContent(String questionContent) {
            this.questionContent = questionContent;
        }
    }
    

      

    import java.util.Observable;
    import java.util.Observer;
    
    
    public class Teacher implements Observer {
        private String teacherName;
    
        public Teacher(String teacherName) {
            this.teacherName = teacherName;
        }
        @Override
        public void update(Observable o,Object arg){
           Course course=(Course)o;
           Question question=(Question)arg;
            System.out.println(teacherName+"老师的"+course.getCourseName()+"课程接收到一个"+question.getUserName()+"提交的问答:"+question.getQuestionContent());
    
        }
    }
    

      

    public class Test {
        public static void main(String[] args) {
            Course course=new Course("Java设计模式精讲");
            Teacher teacher=new Teacher("laoshi");
            course.addObserver(teacher);
    
            Question question=new Question();
            question.setUserName("Geelly");
            question.setQuestionContent("Java");
    
            course.produceQuestion(course,question);
        }
    }
    

      

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  • 原文地址:https://www.cnblogs.com/sunliyuan/p/10789776.html
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