JavaMadeSoEasy.com (JMSE): Program to insert/write content at specific position in file in java

Let’s say c:/myFile.txt looks like this >

you learning file io from javaMadeSoEasy

Write a Program to insert/write content at specific position in file in java, such that after execution of program file must look like this -

you ARE learning file io from javaMadeSoEasy

Java does not allow you to insert in file, so follow these steps >

RandomAccessFile allows us to read/write at random positions by using seek method but when we try to write at random position, data is not inserted, in fact it’s overridden. See How to Read/write from file using RandomAccessFile.

Program to insert/write content at specific position in file in java >

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

public class InsertInFileAtSpecifiedPosition {

public static void main(String[] args) throws IOException {

String fileName = "c:/myFile.txt";

FileReader fr = new FileReader("c:/myFile.txt");

BufferedReader br = new BufferedReader(fr);

// 1) Read from file in String

String str = br.readLine();

// 2) Insert content at specified position in String, as per your

// requirement

String updatedStr = str.substring(0, 4) + "ARE " + str.substring(4);

br.close();

// 3) write updated String in file

FileWriter writer = new FileWriter(fileName);

writer.write(updatedStr);

writer.close();

}

After executing above program c:/myFile.txt will look like this >

you ARE learning file io from javaMadeSoEasy

Labels: Core Java File IO/File handling