显示随机访问文件中的信息

Question

我创建了一个应用程序，允许用户输入他们的账号、余额（不超过99999）和姓氏。程序将获取这些信息，并将其插入到与账号（acct）对应的.txt文件中。这是它的代码：

import java.io.*;
public class NationalBank {
  public static void main(String[] args) throws Exception{
     InputStreamReader temp = null;
     BufferedReader input = null;
     try {
        temp = new InputStreamReader(System.in);
        input = new BufferedReader(temp);
        int acct;
        double amount;
        String name;
        RandomAccessFile file = new RandomAccessFile("bank.txt", "rw");
        while(true) {
            // Asks for input
           System.out.println("Enter Account Number (0-9999): ");
           acct = Integer.parseInt(input.readLine());
           System.out.println("Enter Last Name: ");
           name = input.readLine();
           System.out.println("Enter Balance ");
           amount = Double.parseDouble(input.readLine());
            // Making sure account numbers are between 0 and 9999
           if(acct >=0 && acct <= 9999) {
              file.seek(acct*17);
              file.write(truncateName(name));
              file.writeBytes(" " +amount);
           }
           else {
              continue;
           }
            // Asks user if more entries are needed
           System.out.println("Enter More? (y/n)");   
           if (input.readLine().toLowerCase().equals("n"))
              break;
        }
        file.close();
     }
        catch (Exception e) {  
        }
  }
// Truncate/adding spaces to name until 8 characters
  public static byte[] truncateName (String name) {
     byte[] result = new byte[8];
     for (int i = 0; i < 8; i++)
        result [i] = i < name.length () ? (byte)name.charAt (i) : (byte)' ';
     return result;
  }
}

现在，我正在尝试制作一个应用程序，它将写回所有包含信息的帐户（包括姓氏和余额）。我需要显示这些账户的账号、余额和姓氏。到目前为止，我已经：

import java.io.*;
public class DisplayBank {
  public static void main(String[] args) throws IOException {
    FileInputStream input = new FileInputStream ("bank.txt");
     try {
        byte[] record = new byte[17];
        while (input.read(record) == 17) {
           String name = new String(record, 0, 8);
           long bits = 0;
           for (int i = 8; i < 17; i++) {
              bits <<= 8;
              bits |= record[i] & 0xFF;
           }
           double amount = Double.longBitsToDouble(bits);
           System.out.println("Account Number: " + record + " Name: " + name + ", amount: " + amount);
        }
     }
     catch (IOException e) {  
     }
     finally {
            input.close();
     }
  }
}

这当前仅正确显示名称。余额不正确，我不知道如何获得账号。为了得到帐号，我需要得到name的位置。为了得到amount，我需要寻找name，偏移9个字节，然后读取接下来的8个字节。。。

Answer 1

如果您想解析一个包含姓氏和金额与您提供的内容相似的文本文件：

示例提供的

姓氏93942.12

我要做的是尝试下面的

 public void read_file(){
    try{
    // Open the file that is the first 
    // command line parameter
    FileInputStream fstream = new FileInputStream("C:\Users\Alos\Desktop\test.txt");
    // Use DataInputStream to read binary NOT text.
    BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
    String strLine;
    int record = 0;
    //Read File Line By Line
    while ((strLine = br.readLine()) != null)   {
        String[] splits = strLine.split("t");
        String LastName = splits[0];
        String Amount = splits[1]; 
        System.out.println("Account Number: " + record + " Name: " + LastName + ", amount: " + Amount);
        record++;
    }
    //Close the input stream
    in.close();
      }catch (Exception e){//Catch exception if any
    System.err.println("Error: " + e.getMessage());
    }

}

这可能不是你想要的，但如果你想要不同的东西，请看一看并更新你的问题。

Answer 2

这不是家庭作业，我强烈建议使用一些RDBMS，如Derby或MySQL。