Regular Expression Powerfull sample in java

 We can use regular expression and to do large set of works as simple and single line code .

In this example i will show you how the regular expression play a vital stage .
I want to read a file and insert a new line (\n) at every 100 th character in that file content and write those changes in another file.

Normally what i did first is written a code to read file line by line and written a sample piece of code to read position and insert the new line in that particular position then written in new file.

Instead for write separate function i write an replaceAll with regular expression.

The sample code given below,

package com.shinnedhawks;

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

    public void replace() {
        String oldFileName = "abc.txt";
        String tmpFileName = "abcnew.txt";

        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) {
                line = line.replaceAll("(.{100})", "$1\n"); // Here is the code it simplefied that largest code in single
                bw.write(line);
            }
        } catch (Exception e) {
            return;
        } finally {
            try {
                if(br != null)
                    br.close();
            } catch (IOException e) {
                // handle code
            }
            try {
                if(bw != null)
                    bw.close();
            } catch (IOException e) {
                // handle code
            }
        }
        // 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);

    }
}