How do I add data to text file and not overwrite w

Question

This is my code so far but it overwrites what I have in the text file already. What I want is for it to add it to a new line in the text file.

import java.io.*;
import java.util.Scanner;

public class Login{
  public static void main(String[] args) throws IOException {
    Scanner s1,s2;
    s1 = new Scanner(new FileInputStream("login.txt"));
    s2 = new Scanner(System.in);
    boolean loggedIn = false;
    String name,pword,n,p;
    System.out.println("Are you a new user? (Type y for yes or n for no)");
    String nU = s2.next();

    if (nU.equals("n"))
    {
    System.out.println("Enter username:");
    n=s2.next();
    System.out.println("Enter password:");
    p=s2.next();
    while(s1.hasNext()){
      name=s1.next();
      pword=s1.next();
      if(n.equals(name) && p.equals(pword)){
        System.out.println("You are logged in.");
        loggedIn = true;
        break;
      }
    }
    if(!loggedIn)
      System.out.println("Incorrect password or username.");
    }
    else if (nU.equals("y"))
    {

Down here is where the problem with my code will be as this is where it is writing it to the file.

     PrintWriter out = new PrintWriter("login.txt"); 
     System.out.println("Enter username:");
     n=s2.next();
     System.out.println("Enter password:");
     p=s2.next();
     out.append(n);
     out.append(p);
     out.close();
     System.out.println("Account has been created and you are logged in.");
    }
    else
      System.out.println("Invalid response.");

Answer 1

Very simple example is this.

String workingDir = System.getProperty("user.dir");
System.out.println("Current working directory : " + workingDir);
File file = new File(workingDir+"/WebContent/Files/login.txt");
PrintWriter printWriter = new PrintWriter(new BufferedWriter(new FileWriter(file,true)));
printWriter.println(workingDir);
printWriter.println("Good thing");
printWriter.close();

hope it helps.

Answer 2

It is advised to use chain of BufferedWriter and FileWriter, and the key point is FileWriter will append String to current file when use the one of its constructor that lets appaneding by adding true to last paramter like

new FileWriter("login.txt", true)        

and when we surrounding it with BufferedWriter object in order to be more efficient if you are going to write in the file number of time, so it buffers the string in big chunk and write the big chunk into a file and clearly you can save a lot of time for writing into a file

Note :It is possible not to use BuffredWriter ,but it is advised because of better performance and ability to buffer the big chunk of Strings and write them once

Just change your

PrintWriter out = new PrintWriter("login.txt"); 

to

PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("login.txt", true)));

Example:

try(PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("login.txt", true)));) {
    String data = "This content will append to the end of the file";
    File file = new File("login.txt");
    out.println(data);
} catch(IOException e) {
}

It is possible to solve this issue without using BufferedWriter, yet the performance will be low as I mentioned.

Example:

try (PrintWriter out = new PrintWriter(new FileWriter("login.txt", true));) {
    String data = "This content will append to the end of the file";
    File file = new File("login.txt");
    out.println(data);
} catch (IOException e) {
}

Answer 3

Use FileWriter

FileWriter fw = new FileWriter(filename,true);
//the true will append the new data to the existing data

Something like this

PrintWriter out = new PrintWriter(new BufferedWriter(
                                         new FileWriter("login.txt", true)))
out.println(n);
out.println(p);
out.close();