观察者设计模式及java Demo

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观察者设计模式

1、主题对象管理着某些数据；
2、当主题内的数据改变就会通知观察者(一旦数据发生改变，新的数据会以某种形式送到观察者手上)；
3、观察者已经订阅(注册)主题以便在主题数据改变时能够收到更新；

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/**   
 * @Title: ObserverTest.java 
 * @Package com.primeton.test 
 * @Description: TODO(用一句话描述该文件做什么) 
 * @date 2015年11月6日 下午11:04:07 
 * @version V1.0   
 */
package com.primeton.test;
import java.util.Observable;
import java.util.Observer;
/**
 * @ClassName: ObserverTest
 * @Description: TODO(这里用一句话描述这个类的作用)
 * @author yuechang
 * @date 2015年11月6日 下午11:04:07
 */
public class Test {
	public static void main(String[] args) {
		School school = new School("娄底师专");
		Student studentA = new Student(school.getSchoolName(), "A");
		Student studentB = new Student(school.getSchoolName(), "B");

		school.addObserver(studentA);
		school.addObserver(studentB);

		System.out.println(school);
		System.out.println(studentA);
		System.out.println(studentB);

		// 学校改名了
		school.setSchoolName("湖南人文科技学院");
		school.setChanged();
		school.notifyObservers(school);

		System.out.println(school);
		System.out.println(studentA);
		System.out.println(studentB);
	}
}

class School extends Observable {

	private String schoolName;
	public School() {
	}
	/**
	 * @param schoolName
	 */
	public School(String schoolName) {
		super();
		this.schoolName = schoolName;
	}
	public String getSchoolName() {
		return schoolName;
	}
	public void setSchoolName(String schoolName) {
		this.schoolName = schoolName;
	}
	@Override
	public String toString() {
		return "School [schoolName=" + schoolName + "]";
	}
	@Override
	protected synchronized void setChanged() {
		super.setChanged();
	}
}

class Student implements Observer {

	private String studentName;
	private String schoolName;
	public Student() {
	}

	/**
	 * @param studentName
	 * @param schoolName
	 */
	public Student(String schoolName, String studentName) {
		super();
		this.studentName = studentName;
		this.schoolName = schoolName;
	}
	public String getStudentName() {
		return studentName;
	}
	public void setStudentName(String studentName) {
		this.studentName = studentName;
	}
	public String getSchoolName() {
		return schoolName;
	}
	public void setSchoolName(String schoolName) {
		this.schoolName = schoolName;
	}
	@Override
	public void update(Observable o, Object arg) {

		if (arg instanceof School) {
			this.schoolName = ((School) arg).getSchoolName();
		}
	}
	@Override
	public String toString() {
		return "Student [studentName=" + studentName + ", schoolName=" + schoolName + "]";
	}
}