issue with files reading and processing

[Rahul Noel]

I have a two files,it has accid,txtype,amount. one person accid may exist in another file, task is to read contents from files and storing that values(accid,txtype,amount),then number of threads will access this file depending on the txtype like withdraw or deposit the processing should be done.If it is withdraw it has to check with other files data and balance.How can we achieve this

[Rob Spoor]

Please Use One Thread Per Question. This is basically the same problem as this one.

Considering this thread has more information in it, let's continue here.

[Martijn Verburg]

You'll want to begin by looking at the io or nio packages in Java (nio is the newer (and better?) way to perform file I/O.

[Rahul Noel]

Using I/O only.I am facing difficulty in reading file and separating the strings and storing it in hashMap. please help me.

[Rahul Noel]

  
package com.abc.test;
 
import java.io.*;
import java.util.*;
 

public class  Test
{
public static void main(String[] args) 
{
try
{
Map map=null;
    File file = new File("dir");
            File[] list = file.listFiles();
Thread[] 
    int count=0;
for(count = 0; count < list.length; count++)
    {
    FileReader fr = new FileReader(new File(list)) ;
                BufferedReader br = new BufferedReader(fr);
String data = br.readLine();
                while (data != null)
   { 
   data=br.readLine();
   }
                StringTokenizer token = new StringTokenizer(data);
                while (token.hasMoreTokens()) {
           
                      String accid= st.nextToken();
                      String txtype= st.nextToken();
                      String amount= st.nextToken();
 

   map = new Map();
   map.put("accId", accId);
   map.put("txtype",txtype);
   map.put("amount",amount);
   
   
   }
}
            
          }
   }
         catch (FileNotFoundException e)
    {
    }
            finally{
br.close();
} 
            
 
}
}
 
  

Here,my task is to get files data from no. of files and reading it and separate data like accid,txtype,amt and store it in hashMap. I have to synchronize this data in threads I mean many threads will use this data.

[vipin jos]

I am not sure what you meant by synchronization. Solution as per my understanding is as follows.
If you want to lock the file while a write is in progress, you should be using nio.

try {
File file = new File("a.txt");
FileOutputStream fin = new FileOutputStream(file);
FileChannel fchannel = fin.getChannel();
fchannel.lock();
fin.write(250);
fchannel.force(false);
Thread.sleep(200000);
} catch(Exception e) {
e.printStackTrace();
}

If you run the above code and while it is sleeping, if you try to edit it and save(use textpad or notepad), it would not allow since it is locked by the Thread.

For more information, read through nio and nio.channel packages.