How to write into file in append mode ?

Use FileWriter with append flag = true

Example

File file = new File("hello.txt");

String data = "This content will append to the end of the file";

// true = append file

FileWriter fileWritter = new FileWriter(file.getName(),true);

BufferedWriter bufferWritter = new BufferedWriter(fileWritter);

bufferWritter.write(data);

bufferWritter.close();