删除用户输入的信息

Question

我想为一些作业制作电影数据库。卡住添加删除功能。由于我的moivecount变量，我试图重新添加另一部电影时遇到困难。如果我删除movie3，如果我有4部电影，那么moviecount == 3，当我尝试添加另一部电影时，当我需要添加movie3时，它会再次请求movie4。

import java.util.*; 
public class Interface { 
private void run() 
{ 


    Scanner console = new Scanner(System.in); 
    Movie m1; 
    Movie m2; 
    Movie m3; 
    Movie m4; 

    String name, director; 
    int size, duration, option; 
    int moviecount = 0; 

    m1 = new Movie(); 
    m2 = new Movie(); 
    m3 = new Movie(); 
    m4 = new Movie(); 

do { 
    System.out.println("Import new movie:(0), Delete movie from Database (2), View Movies: (3), Exit (9): "); 
    option = console.nextInt(); 
    switch(option) 
    { 
     case 0: 
     if(moviecount == 0) 
     { 
       System.out.print("First Movie: "); 
       name = console.next(); 
       m1.setName (name); 
       System.out.print("Director: "); 
       director = console.next(); 
       m1.setDirector (director); 
       System.out.print("Size in MB: "); 
       size = console.nextInt(); 
       m1.setSize(size); 
       System.out.print("Duration in minutes: "); 
       duration = console.nextInt(); 
       m1.setDuration(duration); 
       moviecount++; 
       break; 


     } 

     else if(moviecount == 1) 
     { 
       System.out.print("Second Movie: "); 
       name = console.next(); 
       m2.setName (name); 
       System.out.print("Director: "); 
       director = console.next(); 
       m2.setDirector (director); 
       System.out.print("Size in MB: "); 
       size = console.nextInt(); 
       m2.setSize(size); 
       System.out.print("Duration in minutes: "); 
       duration = console.nextInt(); 
       m2.setDuration(duration); 
       moviecount++; 
       break; 
     } 

     else if(moviecount == 2) 
     { 
       System.out.print("Third Movie: "); 
       name = console.next(); 
       m3.setName (name); 
       System.out.print("Director: "); 
       director = console.next(); 
       m3.setDirector (director); 
       System.out.print("Size in MB: "); 
       size = console.nextInt(); 
       m3.setSize(size); 
       System.out.print("Duration in minutes: "); 
       duration = console.nextInt(); 
       m3.setDuration(duration); 
       moviecount++; 
       break; 
     } 

     else if(moviecount == 3) 
     { 
       System.out.print("Fourth Movie: "); 
       name = console.next(); 
       m4.setName (name); 
       System.out.print("Director: "); 
       director = console.next(); 
       m4.setDirector (director); 
       System.out.print("Size in MB: "); 
       size = console.nextInt(); 
       m4.setSize(size); 
       System.out.print("Duration in minutes: "); 
       duration = console.nextInt(); 
       m4.setDuration(duration); 
       moviecount++; 
       break; 
     } 

     else 
     { 
       System.out.print("Too many movies currently stored \n"); 
       break; 
     } 

     case 2: System.out.print("Which movie to delete? (1), (2), (3), (4) \n"); 
     option = console.nextInt(); 
     switch(option) 
     { 
      case 1: m1.setName(null); 
        m1.setDirector(null); 
        m1.setSize(0); 
        m1.setDuration(0); 
        System.out.print("Movie 1 deleted! "); 
        moviecount--; 
        break;   

      case 2: m2.setName(null); 
        m2.setDirector(null); 
        m2.setSize(0); 
        m2.setDuration(0); 
        moviecount--; 
        break; 

      case 3: m3.setName(null); 
        m3.setDirector(null); 
        m3.setSize(0); 
        m3.setDuration(0); 
        moviecount--; 
        break; 

      case 4: m4.setName(null); 
        m4.setDirector(null); 
        m4.setSize(0); 
        m4.setDuration(0); 
        moviecount--; 
        break; 

     } 

     case 3: System.out.print("Movies stored in database: \n"); 
       System.out.print(m1.getName()+"\n"); 
       System.out.print(m2.getName()+"\n"); 
       System.out.print(m3.getName()+"\n"); 
       System.out.print(m4.getName()+"\n"); 










    } 
} 
    while(option!=9); 



} 
public static void main(String[] args){ 
Interface intFace = new Interface(); 
intFace.run(); 
} 
} 

Answer 1

问题在于你的设计。你遇到了这个问题，因为你实际上并不是在任何地方存储电影。您只是创建4个不同的电影对象并将其打印出来。如果您更改了打印语句的顺序，则它们的顺序不同。

你将需要以某种数据结构的添加 - 任何数组，列表，或一些其他类型的集合到你的电影存储在

例如，你可以创建一个List来存储您的电影资料。

//create new List called movieList 
    List movieList = new ArrayList(); 

    //add movies to the list 
    movieList.add(m1); 
    movieList.add(m2); 
    movieList.add(m3); 
    movieList.add(m4); 


    //remove movies from the list by position 
    movieList.remove(0); 
    movieList.remove(1); 
    movieList.remove(2); 
    movieList.remove(3); 

您可以添加您的电影中使用列表的add()方法列表，并使用remove()方法删除它们。请记住，remove会删除您提供的索引处的元素，并且索引将从0开始。

因此，例如要删除第一部电影，您需要调用movieList.remove（0）。 第二部电影将位于索引1等

Answer 2

您的具体实现的答案：您无法使用该moviecount变量来确定您想在哪个插槽中添加新的移动！

取而代之：只是走过你的电影对象。并将数据推入空白的第一个数据。

含义：您可以在Movie类上定义一个“isEmpty（）”方法，如果名称为null，则返回true。

但只是为了记录：拥有和使用这些setter方法是一个坏方法。通常情况下，您会希望使用电影类的构造函数设置所有这些值，因为您不希望稍后更改该信息。

然后您可以简单地做

movie1 = new... 

创建一个新的电影和

movie1 = null 

删除它后来当。然后，您还可以轻松检查是否插入了一个插槽：

if (movie1 == null) {...