Sign Up / Login Array | Java

import javax.swing.JOptionPane;

public class lsArray {
    public static void main(String[] args) {
        byte pil;
        boolean cek = false, error = true;
        int i;
        String[] data = new String[10];

        do {
            if(!cek) {
                JOptionPane.showMessageDialog(null,"Isi data untuk proses login","Sign Up",JOptionPane.INFORMATION_MESSAGE);
                data[0] = JOptionPane.showInputDialog(null,"Masukkan Username :","Sign Up",JOptionPane.QUESTION_MESSAGE); //username
                data[1] = JOptionPane.showInputDialog(null,"Masukkan Password :","Sign Up",JOptionPane.QUESTION_MESSAGE); //password
                cek = true;
            }
            else {
                data[2] = JOptionPane.showInputDialog(null,"Masukkan Username :","Login",JOptionPane.QUESTION_MESSAGE); //username
                data[3] = JOptionPane.showInputDialog(null,"Masukkan Password :","Login",JOptionPane.QUESTION_MESSAGE); //password
                if(data[0].equals(data[2]) && data[1].equals(data[3])){
                    JOptionPane.showMessageDialog(null,"Selamat Anda berhasil login " + data[0] + " :)","Login",JOptionPane.INFORMATION_MESSAGE);
                    error = false;
                }
                else {
                    JOptionPane.showMessageDialog(null,"Login gagal cek sekali lagi","Login",JOptionPane.WARNING_MESSAGE);
                    if(JOptionPane.showConfirmDialog(null,"Anda ingin mencoba login lagi ? ","Login",JOptionPane.YES_NO_OPTION) == JOptionPane.YES_OPTION) {
                        error = true;
                        data[2] = data[3] = " ";
                    }
                    else
                        error = false;
                }
            }

        }while(error);

    }
}