Problem with JScrollPane in Java

The scroll bar will only appear when it's needed. Since you don't have line wrap on, the vertical one will never appear. You should set the FlowLayout before you add your components

ok I added the FlowLayout before the components but it still doesn't show up...

However, if you keep copy and pasting the text. you'll see both scrollbars appear

try this:

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class randomPass {
      public static String gen(int x) {
            String nums = "";
            for (int i = 0; i < x; i++) {
                  nums += (char) ((int) (33 + Math.random() * 94));
            }
            return nums;
      }

      public static void main(String args[]) {
            final String vernum = "v1.2";
            final JTextField in = new JTextField(
                        "Insert the password length here.", 20);
            final JFrame f = new JFrame("Random Password Generator v1.1.0");
            JButton btn = new JButton("Close");
            JPanel p = new JPanel();
            p.add(in);
            p.add(btn);
            final JTextArea out = new JTextArea();
            final JScrollPane scroll = new JScrollPane(out);
            scroll
                        .setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
            f.getContentPane().setLayout(new BorderLayout());
            f.getContentPane().add(BorderLayout.NORTH, p);
            f.getContentPane().add(BorderLayout.CENTER, scroll);
            in.selectAll();
            f.setLocationRelativeTo(null);
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setSize(370, 250);
            f.setVisible(true);
            in.addActionListener(new ActionListener() {
                  public void actionPerformed(ActionEvent e) {
                        String x = in.getText();
                        int b = Integer.parseInt(x);
                        if (b < 1) {
                              JOptionPane
                                          .showMessageDialog(
                                                      null,
                                                      "The password length must be greater than 0, please try again",
                                                      "Random Password Generator " + vernum,
                                                      JOptionPane.ERROR_MESSAGE);
                              in.selectAll();
                        } else {
                                          out.setText("Your random password is :\n\n" + gen(b));
                              in.selectAll();
                        }
                  }
            });
            btn.addActionListener(new ActionListener() {
                  public void actionPerformed(ActionEvent e) {
                        JOptionPane.showMessageDialog(null,
                                    "Thank you for using the Random Password Generator "
                                                + vernum,
                                    "Random Password Generator " + vernum,
                                    JOptionPane.INFORMATION_MESSAGE);
                        f.dispose();
                  }
            });
      }
}

thanks. I tried doing it the way you did it but I didn't know of the setText() method so it didn't work out so well lol.