read from a file, split the line and store in an array JAVA

I think your array is not growing because you are re-declaring for each line of your file (it's in the while loop). To fix that, you could initialize your array before the loop, and use System.arraycopy to make it grow.

A part from this quick fix, there is a number of problems with your idea in my opinion:

• Usernames and passwords should not be stored in a csv file, rather in a database
• Passwords should be hashed and never be visible in clear from the application itself
• The database should be salted
• An array is not the correct data structure to represent key value pairs - you should use a Map for that
• In the occurrence, getting all the usernames/passwords in memory to compare them with a user login is not reasonable. You should hash the pwd provided by the user, find the username in the database, and compare the two hashes

I'm simplifying a bit here, there are tons of literature about that.

Best of luck!

Usually people use an ArrayList for this as apposed to an Array. An array required knowing total number of elements, while an arraylist uses an array underneath and dynamically resizes if necessary (well, creates a bigger array and copies data over).

For the specific case, you actually want a hashmap that takes a key and a value.

   import java.io.BufferedReader;
    import java.io.FileReader;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;

public class BufferedReaderExample {

public static void main(String[] args) {



           try (BufferedReader br = new BufferedReader(new FileReader("Users.csv")))
            {

                String sCurrentLine;
                String first = "Username is: ";
                String second = "Password is: ";
                java.util.HashMap<String,String> data = new java.util.HashMap<String,String>();


                while ((sCurrentLine = br.readLine()) != null) {       
                    String[] information = sCurrentLine.split(",");
                    String username = information[0];
                    String password = information[1];
                    System.out.println(username);
                    System.out.println(password);
                    data.put(username,password);
                    }

            } catch (IOException e) {
                e.printStackTrace();
            } 

        }
    }

When a login comes, you use data.get(username); to get the stored password, and compare with what the user has given.

Declare your array outside the try/catch statement:

    String[] information;
    try (BufferedReader br = new BufferedReader(new FileReader("Users.csv")))
    {

        String sCurrentLine;
        String first = "Username is: ";
        String second = "Password is: ";

        while ((sCurrentLine = br.readLine()) != null) {


            information = sCurrentLine.split(",");
            String username = information[0];
            String password = information[1];
            System.out.println(username);
            System.out.println(password);
        }

    } catch (IOException e) {
        e.printStackTrace();
    }

Then, you'll be able to use the data generated elsewhere.

If you want auto-increment array, Use ArrayList. These are special data structures which increase as the items get added to them.

I would recommend you to create a User POJO class, because tomorrow, if one more property gets added to the rows of CSV, it can be adopted by adding one more field in the below class

class User {

   private String userName;
   private String password;
   //getter :setters

}

and use ArrayList while parsing the file

List<User> userList = new ArrayList<User>();
try (BufferedReader br = new BufferedReader(new FileReader("Users.csv")))
        {

            String sCurrentLine;
            String first = "Username is: ";
            String second = "Password is: ";

            while ((sCurrentLine = br.readLine()) != null) {


                String[] information = sCurrentLine.split(",");
                String username = information[0];
                String password = information[1];

                User u = new User(); 
                u.setUserName(username);
                u.setPassword(password);
                userList.add(u);
            }

        } catch (IOException e) {
            e.printStackTrace();
        } 
}

ALSO: Storing the user's password in a csv file is a security risk. Try using database and store encrypted passwords instead of actual password (while retrieving just decrypt the password and compare)