播放列表管理中添加歌曲会同时添加到主播放列表和普通播放列表中，请老师纠正

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

463

464

465

466

467

468

469

470

471

472

473

474

475

476

477

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

498

499

500

501

502

503

504

package com.imooc.Music;
 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;
import java.util.Map.Entry;
 
//Test类
public class TestDemo {
 
    public void mainMenu() {
        System.out.println("****************************************");
        System.out.println("              **主菜单**");
        System.out.println("              1--播放列表管理");
        System.out.println("              2--播放器管理");
        System.out.println("              0--退出");
        System.out.println("****************************************");
        System.out.println("请输入对应数字进行操作：");
    }
 
    public void playListMenu() {
        System.out.println("****************************************");
        System.out.println("           **播放列表管理**");
        System.out.println("      1--将歌曲添加到主播放列表");
        System.out.println("      2--将歌曲添加到普通播放列表");
        System.out.println("      3--通过歌曲id查询播放列表中的歌曲");
        System.out.println("      4--通过歌曲名称查询播放列表中的歌曲");
        System.out.println("      5--修改播放列表中的歌曲");
        System.out.println("      6--删除播放列表中的歌曲");
        System.out.println("      7--显示播放列表中的所有歌曲");
        System.out.println("      8--导出歌单");
        System.out.println("      9--返回上一级菜单");
        System.out.println("****************************************");
        System.out.println("请输入对应数字对播放列表进行管理：");
    }
 
    public void playerMenu() {
        System.out.println("****************************************");
        System.out.println("              **播放器管理**");
        System.out.println("          1--向播放器添加播放列表");
        System.out.println("          2--从播放器删除播放列表");
        System.out.println("          3--通过名字查询播放列表信息");
        System.out.println("          4--显示所有播放列表名称");
        System.out.println("          9--返回上一级菜单");
        System.out.println("****************************************");
        System.out.println("请输入对应数字对播放器进行操作：");
    }
 
    public static void main(String[] args) {
 
        Scanner sc = new Scanner(System.in);
 
        List<Song> musicList = new ArrayList<Song>();
        PlayList p1 = new PlayList("主播放列表", musicList);
 
        Map<String, PlayList> playListMap = new HashMap<String, PlayList>();
        playListMap.put("主播放列表", p1);
        Set<Entry<String, PlayList>> entrySet = playListMap.entrySet();
        PlayListCollection player = new PlayListCollection(playListMap);
 
        TestDemo t = new TestDemo();
 
        while (true) {
            t.mainMenu();
            int x = sc.nextInt();
            switch (x) {
            case 1: {
                while (true) {
                    t.playListMenu();
                    int y = sc.nextInt();
                    switch (y) {
                    case 1: {
                        System.out.println("请输入要添加的歌曲数量");
                        int num = sc.nextInt();
                        for (int i = 0; i < num; i++) {
                            System.out.println("请输入第" + (i + 1) + "首歌曲：");
                            System.out.println("请输入第" + (i + 1) + "首歌曲的id：");
                            String id = sc.next();
                            System.out.println("请输入第" + (i + 1) + "首歌曲的名称：");
                            String name = sc.next();
                            System.out.println("请输入第" + (i + 1) + "首歌曲的歌手：");
                            String singer = sc.next();
                            Song song = new Song(id, name, singer);
                            p1.addToPlayList(song);
                        }
                        continue;
                    }
                    case 2: {
                        System.out.println("请输入要添加的播放列表名称：");
                        String listName = sc.next();
                        boolean flag = player.search(listName);
                        if (flag) {
                            System.out.println("请输入要添加的歌曲数量");
                            int num = sc.nextInt();
                            while (true) {
                                for (int i = 0; i < num; i++) {
                                    System.out.println("请输入第" + (i + 1) + "首歌曲：");
                                    System.out.println("请输入第" + (i + 1) + "首歌曲的id：");
                                    String id = sc.next();
 
                                    if (p1.getMusicList().get(i).getId().equals(id)) {
                                        player.searchPlayListByName(listName).addToPlayList(p1.searchSongById(id));
                                        continue;
                                    } else {
                                        System.out.println("该歌曲在主播放列表中不存在，请输入该歌曲的其他信息");
                                        System.out.println("请输入第" + (i + 1) + "首歌曲的名称：");
                                        String name = sc.next();
                                        System.out.println("请输入第" + (i + 1) + "首歌曲的歌手：");
                                        String singer = sc.next();
                                        Song song = new Song(id, name, singer);
                                        player.searchPlayListByName(listName).addToPlayList(song);
                                    }
                                }
                                break;
                            }
                        } else
                            System.out.println("该播放列表未找到，请先在播放器中添加该播放列表。");
                        p1.displayAllSong();
                        player.searchPlayListByName(listName).displayAllSong();
                        continue;
                    }
 
                    case 3: {
                        System.out.println("输入播放列表名称：");
                        String listName = sc.next();
                        for (Entry<String, PlayList> entry : entrySet) {
                            if (entry.getKey().equals(listName)) {
                                System.out.println("请输入查询歌曲的id");
                                String id = sc.next();
                                System.out.println("查询到的歌曲信息为：");
                                System.out.println(entry.getValue().searchSongById(id));
                                break;
                            } else
                                System.out.println("该歌曲在" + listName + "中不存在。");
                        }
                        continue;
                    }
                    case 4: {
                        System.out.println("输入播放列表名称：");
                        String listName = sc.next();
                        for (Entry<String, PlayList> entry : entrySet) {
                            if (entry.getKey().equals(listName)) {
                                System.out.println("请输入查询歌曲的名称");
                                String name = sc.next();
                                System.out.println("查询到的歌曲信息为：");
                                System.out.println(entry.getValue().searchSongByName(name));
                                break;
                            } else
                                System.out.println("该歌曲在" + listName + "中不存在。");
                        }
                        continue;
 
                    }
                    case 5: {
                        System.out.println("请输入修改歌曲的id");
                        String id = sc.next();
                        for (Entry<String, PlayList> entry : entrySet) {
                            entry.getValue().updateSong(id);
                        }
                        continue;
                    }
                    case 6: {
                        System.out.println("请输入删除歌曲的id");
                        String id = sc.next();
                        for (Entry<String, PlayList> entry : entrySet) {
                            entry.getValue().deleteSong(id);
                        }
                        continue;
                    }
                    case 7: {
                        for (Entry<String, PlayList> entry : entrySet) {
                            entry.getValue().displayAllSong();
                        }
 
                        continue;
                    }
 
                    case 8:
                        p1.exportPlayList();
                        continue;
                    case 9:
                    }
                    break;
                }
                continue;
            }
 
            // **播放器管理**"
//                 1--向播放器添加播放列表;
//                 2--从播放器删除播放列表;
//                 3--通过名字查询播放列表信息;
//                 4--显示所有播放列表名称;
//                 9--返回上一级菜单;
            case 2: {
                while (true) {
                    t.playerMenu();
                    int y = sc.nextInt();
                    switch (y) {
                    case 1: {
                        System.out.println("请输入要添加的播放列表名称");
                        String listName = sc.next();
                        PlayList p = new PlayList(listName, musicList);
                        player.addPlayList(p);
                        continue;
                    }
                    case 2: {
                        System.out.println("请输入要删除的播放列表名称");
                        String listName = sc.next();
                        for (Entry<String, PlayList> entry : entrySet) {
                            if (entry.getKey().equals(listName))
                                player.deletePlayList(entry.getValue());
                        }
                        continue;
                    }
                    case 3: {
                        System.out.println("请输入要查询的播放列表名称");
                        String listName = sc.next();
                        PlayList ps = player.searchPlayListByName(listName);
                        System.out.println("该播放列表存在，该播放列表的信息为：");
                        System.out.println(ps);
                        continue;
                    }
                    case 4:
                        player.displayPlayListName();
                        continue;
                    case 9:
                    }
                    break;
                }
                continue;
            }
            case 0:
                break;
            }
            break;
        }
    }
}
//song类
public class Song {
    private String id;
    private String name;
    private String singer;
 
    public void setId(String id) {
        this.id = id;
    }
 
    public String getId() {
        return this.id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public String getSinger() {
        return singer;
    }
 
    public void setSinger(String singer) {
        this.singer = singer;
    }
 
    public Song(String id, String name, String singer) {
        this.setId(id);
        this.setName(name);
        this.setSinger(singer);
    }
    public Song() {
        super();
        // TODO Auto-generated constructor stub
    }
 
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((id == null) ? 0 : id.hashCode());
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        result = prime * result + ((singer == null) ? 0 : singer.hashCode());
        return result;
    }
 
    @Override
    public boolean equals(Object obj) {
    if(this==obj)
        return true;
    if(obj.getClass()==Song.class) {
        Song s=(Song)obj;
        return (this.getId().equals(s.getId()))&&(this.getName().equals(s.getName()))&&(this.getSinger().equals(s.getSinger()));
    }
    else return false;
    }
 
    @Override
    public String toString() {
        return "歌曲信息：id为:" + id + "，歌曲名称为：" + name + "，演唱者为：" + singer ;
    }
     
     
     
 
}
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
 
//PlayList类
public class PlayList implements Serializable{
    private String playListName;
    private List<Song> musicList = new ArrayList<Song>();
    Scanner sc = new Scanner(System.in);
 
    public String getPlayListName() {
        return playListName;
    }
 
    public void setPlayListName(String playListName) {
        this.playListName = playListName;
    }
 
    public List<Song> getMusicList() {
        return musicList;
    }
 
    public void setMusicList(List<Song> musicList) {
        this.musicList = musicList;
    }
 
    public PlayList(String playListName, List<Song> musicList) {
        this.setPlayListName(playListName);
        this.setMusicList(musicList);
    }
 
    public PlayList() {
    }
 
    // 添加歌曲到播放列表的方法
    public void addToPlayList(Song song) {
        this.musicList.add(song);
    }
 
    // 显示播放列表歌曲的方法
    public void displayAllSong() {
        System.out.println(this.getPlayListName());
        System.out.println("播放列表中的所有歌曲为：");
        for (int i = 0; i < this.musicList.size(); i++)
            System.out.println((Song)this. musicList.get(i));
    }
 
    // 通过id查询歌曲的方法
    public Song searchSongById(String id) {
        Song song = new Song();
            boolean flag = false;
            for (int i = 0; i < this.musicList.size(); i++) {
                if ((this.musicList.get(i).getId()) .equals(id)) {
                    song = (Song)this. musicList.get(i);
                    flag = true;
                    break;
                }
            }
            if (flag == false) // 编程常犯错误:将赋值当等于 (flag=false)
                System.out.println("未找到该歌曲。");
            return song;
        }
     
 
    // 通过歌名查询歌曲的方法
    public Song searchSongByName(String n) {
        Song song = new Song();
            boolean flag = false;
            for (int i = 0; i < musicList.size(); i++) {
                if ((musicList.get(i).getName()).equals(n)) {
                    song = (Song) musicList.get(i);
                    flag = true;
                    break;
                }
            }
            if (flag == false)
                System.out.println("未找到该歌曲。");
        return song;
    }
 
    // 修改歌曲的方法
    public void updateSong(String id) {
            boolean flag = false;
            for (int i = 0; i < musicList.size(); i++) {
                if ((musicList.get(i).getId()).equals(id)) {
                    flag = true;
                    System.out.println("修改的歌曲信息为：");
                    System.out.println((Song) musicList.get(i));
                    System.out.println("请输入修改后的歌曲名称");
                    (musicList.get(i)).setName(sc.next());
                    System.out.println("请输入修改后的歌曲演唱者");
                    (musicList.get(i)).setSinger(sc.next());
                    System.out.println("修改成功！");
                    break;
                }
            }
            if (flag == false)
                System.out.println("未找到该歌曲。");
    }
 
    // 通过id删除歌曲的方法
    public void deleteSong(String id) {
        for (int i = 0; i < musicList.size(); i++) {
            if((musicList.get(i).getId()).equals(id))
                musicList.remove(i);
        }
        System.out.println("删除后的播放列表为：");
        for (int i = 0; i < musicList.size(); i++) {
        System.out.println((Song)musicList.get(i));
        }
    }
     
    //导出歌单
    public void exportPlayList() {
        try {
            FileOutputStream fos=new FileOutputStream(this.getPlayListName()+"的歌单.txt");
            ObjectOutputStream oos=new ObjectOutputStream(fos);
            oos.writeObject(musicList);
            oos.flush();
            oos.close();
            fos.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
import java.util.Scanner;
 
//PlayListCollection类
public class PlayListCollection {
    Map<String,PlayList> playListMap=new HashMap<String,PlayList>();
     
    public Map<String, PlayList> getPlayListMap() {
        return playListMap;
    }
    public void setPlayListMap(Map<String, PlayList> playListMap) {
        this.playListMap = playListMap;
    }
     
    public PlayListCollection(Map<String, PlayList> playListMap) {
        this.setPlayListMap(playListMap);
    }
    //添加播放列表
    public void addPlayList(PlayList playList) {
        playListMap.put(playList.getPlayListName(), playList);
        }
         
    //删除播放列表
    public void deletePlayList(PlayList playList) {
        playListMap.remove(playList.getPlayListName());
    }
    //通过名字查询播放列表
    public PlayList searchPlayListByName(String playListName) {
        Set<Entry<String, PlayList>> entrySet = playListMap.entrySet();
        PlayList p=new PlayList();
        for(Entry<String, PlayList> entry:entrySet) {
            if(entry.getKey().equals(playListName))
                p=entry.getValue();
        }
        return p;
    }
    public boolean search(String playListName) {
        Set<Entry<String, PlayList>> entrySet = playListMap.entrySet();
        boolean flag=false;
        for(Entry<String, PlayList> entry:entrySet) {
            if(entry.getKey().equals(playListName))
            flag=true;
        }
        return flag;
    }
    //显示所有播放列表名称
    public void displayPlayListName(){
        System.out.println("播放列表名称为:");
        Set<Entry<String, PlayList>> entrySet = playListMap.entrySet();
        for(Entry<String, PlayList> entry:entrySet) {
            System.out.println(entry.getKey());
        }
    }
}

qq_cookies_oqrHNO 2019-03-03

源自：Java常用工具练习 1-5 作业题

收起

1回答

一叶知秋519 回答被采纳获得+3积分 2019-03-04 11:39:08

测试类中同学定义了一个musicList

在创建普通播放列表时，传入的也是这个musicList对象，导致主播放列表和普通播放列表拥有同一个musicList，所以添加歌曲到主播放列表也会同时添加到普通播放列表；

修改建议：PlayList增加一个单参构造方法，为：PlayList pl=new PlayList("主播放列表")；

创建普通播放列表时，也是： PlayList p = new PlayList(listName);

这样在创建播放列表时，就不会拥有同一个musicList了。

祝学习愉快！

收起回答

qq_cookies_oqrHNO 提问者 #1

请问老师，使用单参构造方法创建播放列表时时就直接创建了属于自己的音乐表了吗

2019-03-04 17:02:56
好帮手慕阿满回复提问者 qq_cookies_oqrHNO #2

同学你好，使用这种方式可以创建播放列表，另外可以调用addPlayList()方法将播放列表添加到播放器中。祝：学习愉快~

2019-03-04 19:04:41