How to append content to file in Java

FileWritter, a character stream to write characters to file. By default, it will replace all the existing content with new content, however, when you specified a true (boolean) value as the second argument in FileWritter constructor, it will keep the existing content and append the new content in the end of the file.

1. Replace all existing content with new content.

new FileWriter(file);

2. Keep the existing content and append the new content in the end of the file.

new FileWriter(file,true);

Append file example

A text file named “javaio-appendfile.txt” and contains the following content.

ABC Hello

Append new content with new FileWriter(file,true)

package com.example.file;

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

public class AppendToFileExample 
{
    public static void main( String[] args )
    { 
     try{
      String data = " This content will append to the end of the file";
      
      File file =new File("javaio-appendfile.txt");
      
      //if file doesnt exists, then create it
      if(!file.exists()){
       file.createNewFile();
      }
      
      //true = append file
      FileWriter fileWritter = new FileWriter(file.getName(),true);
             BufferedWriter bufferWritter = new BufferedWriter(fileWritter);
             bufferWritter.write(data);
             bufferWritter.close();
         
         System.out.println("Done");
         
     }catch(IOException e){
      e.printStackTrace();
     }
    }
}