找不到爲什麼數組顯示爲null

我想讀取一個txt文件並將文件中的每條記錄存儲到名爲data []的對象數組中。除了記錄部分沒有在數據[]中正確分配以外，一切正常。找不到爲什麼數組顯示爲null

This is the format for the record.txt... 

4252 4 item1 
2435 23 item2 
4355 16 item3 
so on and so on...

我想繼續使用我一直在使用的方法，即使有一種更簡單的方法（總會有）。

謝謝你了...

import java.util.Scanner; 
    import java.io.*; 


    public class SortsTest 
    { 
     private static Data[] data; 
     private static String file_to_read; 
     private static int num_of_records, 
         current_record = 0; 
     private final static int RECORD_DATA = 3; 
     private static Scanner scan_file1; 

     public static void main(String[] args) throws IOException 
     { 
     try { 

      Scanner scan = new Scanner(System.in); 

      System.out.print("Enter a file name: "); 
      file_to_read = scan.next(); 

      System.out.print("\nInput file = " + file_to_read); 
      System.out.print("\n# of records = "); 
      num_of_records = scan.nextInt(); 

      scan_file1 = new Scanner(new File(file_to_read)); 

      //---------------------- populate data array ------------------------ 
      while (scan_file1.hasNext()) 
      { 
       data = new Data[num_of_records]; 
       String record[] = new String[RECORD_DATA]; 

       for(int i = 0; i < RECORD_DATA; i++) 
       { 
        String line = scan_file1.next(); 
        record[i] = line; 
       } 
       data[current_record] = new Data(record[0],record[1], record[2]); 
       current_record++; 
      } 
      //-------------------------------------------------------------------- 

      //System.out.print("\n\nRecord 10: " + data[10].getPartName() + " " + data[10].getQuantity() + " " + data[10].getPartNumber()); 
      System.out.print("\n\nRecord 10: " + data[10]); 

     } 
     catch (FileNotFoundException e) 
     { 
      e.printStackTrace(); 
     } 

     } 
    } 

    ///////////////////////////// Data file ///////////////////////////////// 

    import java.util.Scanner; 
    import java.io.*; 


    public class Data 
    { 

     private int part_num, 
        quantity; 
     private String part_name; 
     private Scanner scan_file1; 


     public Data(String part, String quan, String name) 
     { 
      part_num = Integer.parseInt(part); 
      quantity = Integer.parseInt(quan); 
      part_name = name; 
     } 


     public void setPartNumber(int num) 
     { 
      part_num = num; 
     } 

     public void setQuantity(int quan) 
     { 
      quantity = quan; 
     } 

     public void setPartName(String name) 
     { 
      part_name = name; 
     } 

     public int getPartNumber() 
     { 
      return part_num; 
     } 

     public int getQuantity() 
     { 
      return quantity; 
     } 

     public String getPartName() 
     { 
      return part_name; 
     } 


    }

來源

2011-11-12 aStackofQueues

使用eclipse來調試你的代碼 - 在第1行設置一個斷點並逐行檢查每個變量。你會很快發現問題。 – Bohemian

沒有去太深到您的代碼，我懷疑這是你的問題的一部分：

//---------------------- populate data array ------------------------ 
while (scan_file1.hasNext()) 
{ 
    // you recreate your array every loop iteration 
    data = new Data[num_of_records];

相反，你需要做到以下幾點：

//---------------------- populate data array ------------------------ 
data = new Data[num_of_records];   
while (scan_file1.hasNext()) 
{

來源

2011-11-12 20:29:45 mcfinnigan

通過while循環每次迭代創建一個新的空數據數組，請嘗試以下操作：

 data = new Data[num_of_records]; 
     while (scan_file1.hasNext()) 
     {

來源

2011-11-12 20:30:09 rsp

哇...我的笑話非常感謝... – aStackofQueues

找不到爲什麼數組顯示爲null

回答

相關問題