import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;

public class TestingWindow {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new JFrame();
                frame.setBounds(100, 100, 150, 200);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                JScrollPane scrollPane = new JScrollPane();
                frame.getContentPane().add(scrollPane, BorderLayout.CENTER);

                JPanel panel = new JPanel();
                GridBagLayout gbl_panel = new GridBagLayout();
                panel.setLayout(gbl_panel);
                scrollPane.setViewportView(panel);

                GridBagConstraints gbc = new GridBagConstraints();
                gbc.gridwidth = GridBagConstraints.REMAINDER;
                gbc.anchor = GridBagConstraints.NORTH;
                gbc.weightx = 1;

                gbc.fill = GridBagConstraints.HORIZONTAL;

                JPanel panelToAdd = new JPanel();
                JLabel label = new JLabel("Test 1");
                panelToAdd.setBackground(Color.blue);
                panelToAdd.add(label);
                panelToAdd.setAlignmentY(Component.TOP_ALIGNMENT);
                panel.add(panelToAdd, gbc, -1);
                panel.revalidate();

                JPanel panelToAdd2 = new JPanel();
                JLabel label2 = new JLabel("Test 2");
                panelToAdd2.setBackground(Color.green);
                panelToAdd2.add(label2);
                panel.add(panelToAdd2, gbc, -1);
                panel.revalidate();

                JPanel panelToAdd3 = new JPanel();
                JLabel label3 = new JLabel("Test 3");
                panelToAdd3.setBackground(Color.yellow);
                panelToAdd3.add(label3);
                panel.add(panelToAdd3, gbc, -1);
                panel.revalidate();
                frame.setVisible(true);
            }
        });
    }

}