Question

我想读取一个txt文件并将文件中的每条记录存储到一个名为data []的对象数组中。除了在数据[]中没有正确分配记录部分外，一切正常。

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

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

我想继续使用我一直在使用的方法，即使有更简单的方法（总是存在）。

非常感谢...

   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;
        }


    }

Answer 1

通过while循环每次迭代都会创建一个新的空数据数组，请尝试：

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

Answer 2

如果不深入您的代码，我怀疑这是您的问题的一部分：

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

相反，您需要执行以下操作：

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

无法弄清楚为什么数组显示为null

2 个答案: