Jscrollbar swing

bar.setValue(bar.getMaximum()-bar.getVisibleAmount())

import javax.swing.UIManager;

public static void main(String[] args)
{
    try
    {
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    }
    catch (Exception e)
    {
        // en cas de problème, les paramètres par défaut sont conservés
    }
        
    // ...
}

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

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JScrollBar;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;

public class Test
{
    public static void main(String[] args)
    {
        JFrame frame = new JFrame();
        frame.setBounds(100, 100, 100, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(new BorderLayout(0, 0));
        
        JButton btnHaut = new JButton("Haut");
        frame.getContentPane().add(btnHaut, BorderLayout.NORTH);
        
        JButton btnBas = new JButton("Bas");
        frame.getContentPane().add(btnBas, BorderLayout.SOUTH);
        
        JScrollPane scrollPane = new JScrollPane();
        frame.getContentPane().add(scrollPane, BorderLayout.CENTER);
        
        JTextPane textPane = new JTextPane();
        scrollPane.setViewportView(textPane);
        
        StringBuilder sb = new StringBuilder();
        for (int i = 1; i <= 100; i++ )
            sb.append(i + "\n");
        textPane.setText(sb.toString());
        
        final JScrollBar bar = scrollPane.getVerticalScrollBar();
        
        btnHaut.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                bar.setValue(bar.getMinimum());
            }
        });
        
        btnBas.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                bar.setValue(bar.getMaximum() - bar.getVisibleAmount());
            }
        });
        
        frame.setVisible(true);
    }    
}