修改Java中的现有文件内容 [英] Modifying existing file content in Java

问题描述

我想替换第二行文件内容，可以根据以下文件格式和侦听器方法来帮助请求。

I want to replace the second line file content, can somebody help please based on the below file format and listener method.

1324254875443
1313131
Paid
0.0

第二行长并且要替换为 currentTimeMillis（）。

2nd line is long and want to replace to currentTimeMillis().

/************** Pay Button Listener **************/
public class payListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {

        ArrayList<String> lines = new ArrayList<String>();
        String line = null;

        try {
            FileReader fr = new FileReader("Ticket/" + ticketIDNumber + ".dat");
            BufferedReader br = new BufferedReader(fr);
            FileWriter fw = new FileWriter("Ticket/" + ticketIDNumber + ".dat");
            BufferedWriter bw = new BufferedWriter(fw);
            while ((line = br.readLine()) != null) {
                if (line.contains("1313131"))
                    line.replace(System.currentTimeMillis();
                lines.add(line);
                bw.write(line);
            }  //end if                 

        }     //end try
        catch (Exception e) {

        }  //end catch   
    }    //end while
}//end method

推荐答案

如接受的答案 类似的问题：

同时以书面形式打开一个临时文件，每行读取，必要时进行修改，然后写入临时文件，最后删除原始和重命名临时文件。

open a temporary file in writing mode at the same time, and for each line, read it, modify if necessary, then write into the temporary file. At the end, delete the original and rename the temporary file.

基于你的实现，类似于：

Based on your implementation, something similar to:

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class ReplaceFileContents {
   public static void main(String[] args) {
     new ReplaceFileContents().replace();
   }

   public void replace() {
      String oldFileName = "try.dat";
      String tmpFileName = "tmp_try.dat";

      BufferedReader br = null;
      BufferedWriter bw = null;
      try {
         br = new BufferedReader(new FileReader(oldFileName));
         bw = new BufferedWriter(new FileWriter(tmpFileName));
         String line;
         while ((line = br.readLine()) != null) {
            if (line.contains("1313131"))
               line = line.replace("1313131", ""+System.currentTimeMillis());
            bw.write(line+"\n");
         }
      } catch (Exception e) {
         return;
      } finally {
         try {
            if(br != null)
               br.close();
         } catch (IOException e) {
            //
         }
         try {
            if(bw != null)
               bw.close();
         } catch (IOException e) {
            //
         }
      }
      // Once everything is complete, delete old file..
      File oldFile = new File(oldFileName);
      oldFile.delete();

      // And rename tmp file's name to old file name
      File newFile = new File(tmpFileName);
      newFile.renameTo(oldFile);

   }
}

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