Variable Layout in Swing

MiGLayout has a lot of appeal, but BoxLayout is an alternative.

import java.awt.*;
import java.util.List;
import java.util.ArrayList;
import javax.swing.*;

public class BoxTest extends JPanel {

    private List<JTextField> fields = new ArrayList<JTextField>();

    public BoxTest() {
        this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
        this.add(createPane(3, "One ", Color.red));
        this.add(createPane(3, "Two ", Color.green));
        this.add(createPane(10, "Three ", Color.blue));
    }

    private JPanel createPane(int n, String s, Color c) {
        JPanel outer = new JPanel();
        outer.setLayout(new BoxLayout(outer, BoxLayout.Y_AXIS));
        outer.setBorder(BorderFactory.createLineBorder(c, 2));
        for (int i = 0; i < n; i++) {
            JPanel inner = new JPanel();
            inner.setLayout(new BoxLayout(inner, BoxLayout.X_AXIS));
            JLabel label = new JLabel(s + i + ":", JLabel.RIGHT);
            label.setPreferredSize(new Dimension(80, 32));
            inner.add(label);
            JTextField tf = new JTextField("Stackoverflow!", 32);
            inner.add(tf);
            fields.add(tf);
            outer.add(inner);
        }
        return outer;
    }

    private void display() {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JScrollPane jsp = new JScrollPane(this,
            JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
            JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        this.validate();
        Dimension d = this.getPreferredSize();
        d.height /= 2;
        jsp.getViewport().setPreferredSize(d);
        jsp.getVerticalScrollBar().setUnitIncrement(
            this.getPreferredSize().height / fields.size());
        f.add(jsp);
        f.pack();
        f.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new BoxTest().display();
            }
        });
    }
}

I would look at miglayout. It's a lot more useful than any of the inbuilt layout managers.

Your general goal - "usable component sizes" clashes with "unknown number". Make the number large enough and they won't fit any screen.

Overthink if you wouldn't be better off with using JTables (cells can be made editable) in conjuction with a JScrollPanel. If you want/must keep your approach of generating components, put the whole JPanel that contains your components into a JScrollPane, that way the components wont be squeezed to badly.

Yeah, MiGLayout is nice. You can do pretty much anything with it.