查找具有相同名称的数组中的对象索引，按值对它们进行排序，然后更改它们的值

3 回答

• 0

  考虑以下策略：

  • 遍历数组中的每个book对象，并检查它是否与用户输入匹配 .

  • 如果图书匹配，请将其存储为第一遍案例的初始值's index in an array for later use and update the value for a global min price variable if the book has a lower price than what it was previously set to (control it' s）

  • 完成列表的迭代后，使用存储每个匹配书籍索引的数组，并使用全局最小价格变量更新其价格字段

  回复于 2024-05-18T23:42:21+08:00
• 0

  感谢大家的帮助，我想出了如何让我的程序在Jeff Ward和Phillip的帮助下做我想做的事 . 新的WORKING代码如下！ :)

  //Beginning of ModifyBooks Class
      Books[] Library = new Books[10];
  
      Library[0] = new Books();
      Library[1] = new Books("Lovely Bones", 12345, 20);
      Library[2] = new Books("Birds in a Fence", 123456, 13);
      Library[3] = new Books("Hunger Games", 1234567, 14);
      Library[4] = new Books("Titanic", 12345678, 12);
      Library[5] = new Books("Heroes", 123456789, 21);
      Library[6] = new Books(Library[0]);
      Library[7] = new Books(Library[0]);
      Library[8] = new Books(Library[2]);
      Library[9] = new Books(Library[3]);
  
      //Changing all prices of books
      for (int i = 0 ; i < Library.length ; i++){
          Library[i].price = i + 5;
      }
  
      //Keyboard configuration
      Scanner kb = new Scanner(System.in);
  
      //Getting user information
      System.out.println("Please enter a book's title:");
      String UserTitle = kb.nextLine();
  
      System.out.println("Please enter a book's ISBN Number:");
      int UserISBN = kb.nextInt();
  
      System.out.println("Your entered book's title is " + UserTitle + " and the ISBN is " + UserISBN);
  
      int[] sameBook = new int[10]; //new array that will carry the index of each match
      int counter = 0; //tracks number of matches
      int globalMin = 200; //lowest price for the matches books, initialized at 200 so the program functions properly
  
  
      //Finding the matches in main array, and casting their indexes in another array
      for (int i = 0 ; i < Library.length ; i++ ){
          if (UserTitle.equalsIgnoreCase(Library[i].title) && UserISBN == Library[i].ISBN){
              sameBook[i] = i;
              counter++;
                  if (Library[i].price < globalMin){
                      globalMin = Library[i].price;
                  }
          }
          else {
              sameBook[i] = 0;
          }
  
      }
  
      //Creating a new array that only contains the amount of matches there are, containing their indexes
      int[] smallerLibrary = new int[counter];
      int j = 0;
  
      for (int i = 0 ; i < sameBook.length ; i++){
          if (sameBook[i] != 0){
              smallerLibrary[j++] = sameBook[i];
          }
      }
  
      //Text notifying user of matches and telling the, what the new prices will be
      for (int i = 0 ; i < smallerLibrary.length ; i++){
          System.out.println("Index number [" + smallerLibrary[i] + "] matches both the ISBN and title. The price was $" + Library[smallerLibrary[i]].price + " and is being changed to the lowest price of $" + globalMin + ".");
      }
  
      //Changing the prices from the matches to the lowest prices
      for (int i = 0 ; i < Library.length ; i++){
          if (UserTitle.equalsIgnoreCase(Library[i].title) && UserISBN == Library[i].ISBN){
          Library[i].price = globalMin;
          System.out.println("Change was made for index number "+i+".");
          }
      }
  

  回复于 2024-05-18T23:42:21+08:00
• 0

  问题是你正在迭代不同长度的数组导致ArrayIndexOutOfBounds .

  如果您输入“Lovely Bones”，111112，那么您将有3个匹配 .

  sameBook长度总是10 .

  double[] sameBook = new double[10];
  

  但是SmallerLibrary长度为3（用计数器初始化）

  double[] SmallerLibrary = new double[counter];
  

  因此，当迭代sameBook.length时，索引最终将大于SmallerLibrary.length，从而导致异常 .

  for (int i = 0 ; i < sameBook.length ; i++){
      if (sameBook[i] != 0){
          SmallerLibrary[i] = sameBook[i];  // Exception thrown here
      }
  }
  

  您需要为SmallerLibrary中的值指定单独的索引 .

  for (int i = 0, j = 0; i < sameBook.length; i++) {
       if (sameBook[i] != 0) {
          SmallerLibrary[j++] = sameBook[i];
       }
    }
  

  回复于 2024-05-18T23:42:21+08:00