package bookstoreex; import java.util.ArrayList; import java.util.List; /** * Created by Administrator on 2017/6/16. */ public class Student implements DisplayElement , Observer { private String name; private List hasBooks; private Observable observable; public Student(String name,Observable observable) { this.name = name; this.hasBooks = new ArrayList<>(); this.observable = observable; observable.registerObserver(this); } @Override public void update(String book) { hasBooks.add(book); System.out.print(name+"买到了书<"+book+"> "); display(); } @Override public void display() { System.out.println(name+"有书->"+hasBooks.toString()); } }