How to add data without overwriting the existing data?

Question

I am creating a daily savings log application.

the files I am using overwrites existing data. I need a solution in which the files can be updated without overwriting existing data.

Here's the code I'm working on;

for writing the data:

private static void write(int cur_bal,int amt ,int flag) throws IOException
    {
        File file = new File("bal.txt"); 
        log= new BufferedWriter(new FileWriter("log.txt"));//writer for log
        bal= new BufferedWriter(new FileWriter(file));// "      "  bal
        Scanner File = new Scanner(file);
       SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");  
      Date date = new Date(); 
      String stat ="";
      int balance=0;
      switch(flag)
      {
      case 1:
      {stat="Added";
      balance = cur_bal+amt;
      break;}
      case 2:
      {stat="Removed";
      balance = cur_bal-amt;
      break;}     
      }
      
      String inf=sdf.format(date)+"   "+amt+" ("+stat+")";
      System.out.println(inf);
      System.out.println(balance);
      bal.write(balance+"\n");
      log.write(inf+"\n");
      bal.close();
      log.close();
    }

for reading the file:

private static int bal_read() throws IOException
    {
        FileReader fr=new FileReader("bal.txt");
        int i,balance=0;
        while((i=fr.read())!=-1)  
            balance =  i;
        
        fr.close();
        return (balance);
    }

Answer 1

如果 FileWriter 是以追加模式创建的，则 BufferedWriter 可以追加到文件中： new FileWriter(file, true)

Answer 2

One solution -

PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter("file.txt", true)));
pw.println("some text");
pw.close();

Another way is to create new FileWriter(file, true) - The second parameter true enables append mode.

However you should use logging frameworks like Log4j for maintaining logs.