Prevent JPanel within JScrollPane from growing horizontally

Question

I have a JPanel with FlowLayout that I'm dynamically filling with identical components (JButtons in the MWE). The JPanel is inside a JScrollPane. As I add components, I'd like them to fill left to right, kicking down to the next row once the top row would become wider than the JScrollPane.

My problem is that FlowLayout is instead widening the JPanel ad nauseum, to which the JScrollPane responds by adding a horizontal scroll. How do I prevent this?

Edit: I've seen WrapLayout; I was hoping for a solution within standard Java since I'm using NetBeans GUI Builder for my application.

MWE based on this answer:

import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JPanel;

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

import java.awt.*;
import javax.swing.JScrollPane;

public class MWE extends JFrame implements ActionListener {

    JPanel panel;
    JScrollPane pane;

    public MWE() {
        super("Add component on JFrame at runtime");
        setLayout(new BorderLayout());

        this.panel = new JPanel();
        this.pane = new JScrollPane();
        this.panel.setLayout(new FlowLayout(FlowLayout.LEFT));
        this.pane.setViewportView(this.panel);
        add(pane, BorderLayout.CENTER);

        JButton button = new JButton("CLICK HERE");
        add(button, BorderLayout.SOUTH);
        button.addActionListener(this);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(500, 500);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent evt) {
        this.panel.add(new JButton("Button"));
        this.panel.revalidate();
        validate();
    }

    public static void main(String[] args) {
        MWE mwe = new MWE();
    }
}

Answer 1

Try setting a preferred size for the panel :

this.panel.setPreferredSize(new Dimension(500, 500));