求大牛帮忙解决一个课本的例题，源代码却有错误

[Ksly_Tkol]

题目：有一个音像店出租电影业务，需要编写一个应用程序进行管理，在进行出租时能够很快找到顾客需要的电影。例如，在实际应用中，可能会通过以下方式查找需要的电影：
通过标题（title）查找电影
可将电影分成不同的类型（type），如喜剧片、战斗片等。因此在进行出租时，可在某一特定的类型中查找电影；
查找包括某一演员（actor/actress）的电影

代码：
电影类Moive:

import java.util.*; 
public class Movie {
	private String title,type;
	private Vector<String>actors;
	public String getTitle(){
		return title;
	}
	public String getType(){
		return type;
	}
	public Vector<String>getActors(){
		return actors;
	}
	public void setTitle(String aTitle){
		title=aTitle;
	}
	public void setType(String aType){
		type=aType;
	}
	public Movie(){
		this("???","???");
	}
	public Movie(String aTitle,String aType){
		title=aTitle;
		type=aType;
		actors=new Vector<String>();
	}
	@Override
	public String toString(){
		return ("Movie:"+"\""+title+"\"");
	}
	public void addActor(String anActor){
		actors.add(anActor);
	}
}

MovieStore类：

import java.util.*;

public class MovieStore {
	private Hashtable movieList, actorList, typeList;

	public Hashtable getMovieList() {
		return movieList;
	}

	public Hashtable getActorList() {
		return actorList;
	}

	public Hashtable getTypeList() {
		return typeList;
	}

	public MovieStore() {
		movieList = new Hashtable();
		actorList = new Hashtable();
		typeList = new Hashtable();
	}

	public String toString() {
		return ("MovieStore with" + movieList.size() + "movies.");
	}

	public void addMovie(Movie aMovie) {
		movieList.put(aMovie.getTitle(), aMovie);
		if (!typeList.containsKey(aMovie.getType())) {
			typeList.put(aMovie.getType(), new Vector<Movie>());
		}
		((Vector<Movie>) typeList.get(aMovie.getType())).add(aMovie);
		for (String anActor : aMovie.getActors()) {
			if (!actorList.containsKey(anActor)) {
				actorList.put(anActor, new Vector<Movie>());
			}
			((Vector<Movie>) actorList.get(anActor)).add(aMovie);
		}
	}

	public void removeMovie(Movie aMovie) {
		movieList.remove(aMovie.getTitle());
		((Hashtable) typeList.get(aMovie.getType())).remove(aMovie);
		if (!((Hashtable) typeList.get(aMovie.getType())).isEmpty()) {
			typeList.remove(aMovie.getType());
		}
		for (String anActor : aMovie.getActors()) {
			((Vector<Movie>) actorList.get(anActor)).removeElement(aMovie);
			if (!((Hashtable) actorList.get(anActor)).isEmpty()) {
				actorList.remove(anActor);
			}
		}
	}
	
	public void removeMovie(String aTitle){
		if(movieList.get(aTitle)==null){
			System.out.println("No movie with that title");
		}else{
			removeMovie((Movie) movieList.get(aTitle));
		}
	}

	private void removeMovie(Vector<Movie> vector) {
		// TODO Auto-generated method stub
		
	}

	public void listMovies(){
		Enumeration<String>titles=movieList.keys();
		while(titles.hasMoreElements()){
			System.out.println(titles.nextElement());
		}
	}
	
	public void listMoviesWithActor(String anActor){
		Iterator<Movie>someMovies=((AbstractList<Movie>) actorList.get(anActor)).iterator();
		while(someMovies.hasNext()){
			System.out.println(someMovies.next());
		}
	}
	
	public void listMoviesOfType(String aType){
		Vector<Movie>someMovies=(Vector<Movie>) typeList.get(aType);
		for(Movie m:someMovies){
			System.out.println(m);
		}
	}
}

测试类：

public class MovieStoreTester {
	public static void main(String args[]){
			MovieStore aStore=new MovieStore();
			Movie aMovie=new Movie("白毛女","悲剧片");
			aMovie.addActor("田华");
			aMovie.addActor("李百万");
			aMovie.addActor("陈强");
			aStore.addMovie(aMovie);
			
			aMovie=new Movie("党的女儿","教育片");
			aMovie.addActor("田华");
			aMovie.addActor("陈戈");
			aStore.addMovie(aMovie);
			
			aMovie=new Movie("红色娘子军","教育片");
			aMovie.addActor("祝希娟");
			aMovie.addActor("王心刚");
			aMovie.addActor("陈强");
			aStore.addMovie(aMovie);
			
			aMovie=new Movie("五朵金花","爱情片");
			aMovie.addActor("陈丽坤");
			aMovie.addActor("赵丹");
			aStore.addMovie(aMovie);
			
			aMovie=new Movie("上甘岭","战斗片");
			aMovie.addActor("陈强");
			aMovie.addActor("高宝成");
			aStore.addMovie(aMovie);
			
			aMovie=new Movie("马路天使","喜剧片");
			aMovie.addActor("赵丹");
			aMovie.addActor("周璇");
			aStore.addMovie(aMovie);
			
			aMovie=new Movie("少林寺","武打片");
			aMovie.addActor("葛优");
			aStore.addMovie(aMovie);
			
			aMovie=new Movie("我的父亲母亲","爱情片");
			aMovie.addActor("章子怡");
			aMovie.addActor("孙红雷");
			aStore.addMovie(aMovie);
			
			aMovie=new Movie("红高粱","艺术片");
			aMovie.addActor("巩俐");
			aMovie.addActor("姜文");
			aStore.addMovie(aMovie);
			
			System.out.println("Here are the movies in :"+aStore);
			System.out.println("删除白毛女");
			aStore.removeMovie("白毛女");
			System.out.println("删除秋菊打官司");
			aStore.removeMovie("秋菊打官司");
			
			System.out.println("\n教育片");
			aStore.listMoviesOfType("教育片");
			System.out.println("\n爱情片");
			aStore.listMoviesOfType("爱情片");
			
			System.out.println("\n陈强的电影：：");
			aStore.listMoviesWithActor("陈强");
			System.out.println("\n赵丹的电影：：");
			aStore.listMoviesWithActor("赵丹");
	}
}

错误在于MovieStore中的removeMovie方法！

[笑莫问]

报错了就贴异常

[xingfuzhuzi1314]

package com.test;

import java.util.AbstractList;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Vector;

public class MovieStore {
	private Hashtable movieList, actorList, typeList;

	public Hashtable getMovieList() {
		return movieList;
	}

	public Hashtable getActorList() {
		return actorList;
	}

	public Hashtable getTypeList() {
		return typeList;
	}

	public MovieStore() {
		movieList = new Hashtable();
		actorList = new Hashtable();
		typeList = new Hashtable();
	}

	public String toString() {
		return ("MovieStore with" + movieList.size() + "movies.");
	}

	public void addMovie(Movie aMovie) {
		movieList.put(aMovie.getTitle(), aMovie);
		if (!typeList.containsKey(aMovie.getType())) {
			typeList.put(aMovie.getType(), new Vector<Movie>());
		}
		((Vector<Movie>) typeList.get(aMovie.getType())).add(aMovie);
		for (String anActor : aMovie.getActors()) {
			if (!actorList.containsKey(anActor)) {
				actorList.put(anActor, new Vector<Movie>());
			}
			((Vector<Movie>) actorList.get(anActor)).add(aMovie);
		}
	}

	public void removeMovie(Movie aMovie) {
		movieList.remove(aMovie.getTitle());
		((Vector) typeList.get(aMovie.getType())).remove(aMovie);
		if (!((Vector) typeList.get(aMovie.getType())).isEmpty()) {
			typeList.remove(aMovie.getType());
		}
		for (String anActor : aMovie.getActors()) {
			((Vector<Movie>) actorList.get(anActor)).removeElement(aMovie);
			if (!((Vector) actorList.get(anActor)).isEmpty()) {
				actorList.remove(anActor);
			}
		}
	}
	
	public void removeMovie(String aTitle){
		if(movieList.get(aTitle)==null){
			System.out.println("No movie with that title");
		}else{
			removeMovie((Movie) movieList.get(aTitle));
		}
	}

	private void removeMovie(Vector<Movie> vector) {
		// TODO Auto-generated method stub
		
	}

	public void listMovies(){
		Enumeration<String>titles=movieList.keys();
		while(titles.hasMoreElements()){
			System.out.println(titles.nextElement());
		}
	}
	
	public void listMoviesWithActor(String anActor){
		if(actorList.get(anActor)!=null){
			Iterator<Movie>someMovies=((AbstractList<Movie>) actorList.get(anActor)).iterator();
			while(someMovies.hasNext()){
				System.out.println(someMovies.next());
			}
		}
		
	}
	
	public void listMoviesOfType(String aType){
		Vector<Movie>someMovies=(Vector<Movie>) typeList.get(aType);
		for(Movie m:someMovies){
			System.out.println(m);
		}
	}
}

LZ，修改后的类。 遇到错误，你可以自己用debug as进行调试，一共有2个错误。 第一个是把vector强制转换成了hashTable，

public void removeMovie(Movie aMovie) {
		movieList.remove(aMovie.getTitle());
		((Vector) typeList.get(aMovie.getType())).remove(aMovie);
		if (!((Vector) typeList.get(aMovie.getType())).isEmpty()) {
			typeList.remove(aMovie.getType());
		}
		for (String anActor : aMovie.getActors()) {
			((Vector<Movie>) actorList.get(anActor)).removeElement(aMovie);
			if (!((Vector) actorList.get(anActor)).isEmpty()) {
				actorList.remove(anActor);
			}
		}
	}

这个里面， 还有一个，就是在你删除陈强这个的时候，由于对应的白毛女和教育片上面已经删除， 之后获取他对应的电影的时候，为空，可你对于空进行了迭代，导致空指针异常。

public void listMoviesWithActor(String anActor){
		if(actorList.get(anActor)!=null){
			Iterator<Movie>someMovies=((AbstractList<Movie>) actorList.get(anActor)).iterator();
			while(someMovies.hasNext()){
				System.out.println(someMovies.next());
			}
		}
		
	}

[abc41106]

typeList.get获取到的是Vector<Movie>，所以强转类型应该是Vector<Movie>

	public void removeMovie(Movie aMovie) {
		movieList.remove(aMovie.getTitle());
		((Vector<Movie>) typeList.get(aMovie.getType())).remove(aMovie);//
		if (!((Vector<Movie>)typeList.get(aMovie.getType())).isEmpty()) {//为什么我觉得这里应该是isEmpty()而不应该是!isEmpty()呢
			typeList.remove(aMovie.getType());
		}
		for (String anActor : aMovie.getActors()) {
			((Vector<Movie>) actorList.get(anActor)).removeElement(aMovie);//
			if (!((Vector<Movie>) actorList.get(anActor)).isEmpty()) {//为什么我觉得这里应该是isEmpty()而不应该是!isEmpty()呢
				actorList.remove(anActor);
			}
		}
	}

[PHP开发学习门户]

引用 3 楼 abc41106 的回复:

typeList.get获取到的是Vector<Movie>，所以强转类型应该是Vector<Movie> Java code?12345678910111213public void removeMovie(Movie aMovie) { movieList.remove(aMovie.getTitle()); ((Vector<Movie>) typeL……

百度一下吧 isEmpty（）没有值的时候才返回true

[abc41106]

引用 4 楼 Ksly_Tkol 的回复:

引用 3 楼 abc41106 的回复:typeList.get获取到的是Vector<Movie>，所以强转类型应该是Vector<Movie> Java code?12345678910111213public void removeMovie(Movie aMovie) { movieList.remove(aMovie.getTitle()); ((……

。。。我知道啊。。。 我的意思就是没有值的时候才把这个项删掉啊。。。要不然不是把别人的给删了？。。。。。

[abc41106]

	public void removeMovie(Movie aMovie) {
		movieList.remove(aMovie.getTitle());
		((Vector<Movie>) typeList.get(aMovie.getType())).remove(aMovie);//下面只要不是空都删了，剩下的都是空，还要这句干啥使？
		if (!((Vector<Movie>)typeList.get(aMovie.getType())).isEmpty()) {//!isEmpty()就是不为空的时候移除。也就是我删除"白毛女"的时候就得删除"悲剧片"？合理么？
			typeList.remove(aMovie.getType());
		}
		for (String anActor : aMovie.getActors()) {
			((Vector<Movie>) actorList.get(anActor)).removeElement(aMovie);//
			if (!((Vector<Movie>) actorList.get(anActor)).isEmpty()) {//同理，删除"白毛女"的时候就得删除"陈强"？合理么？
				actorList.remove(anActor);
			}
		}
	}

唉，居然让我百度。。。。 太桑心了。。。 好歹也要说google啊。。。。