Java SE (Java Platform, Standard Edition)

import java.awt.BorderLayout;

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

public class MainClass {
  static void addIt(JTabbedPane tabbedPane, String text) {
    JLabel label = new JLabel(text);
    JButton button = new JButton(text);
    JPanel panel = new JPanel();
    tabbedPane.addTab(text, panel);
  }

  public static void main(String[] args) {
    JFrame f = new JFrame("JTabbedPane Sample");
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JTabbedPane tabbedPane = new JTabbedPane( JTabbedPane.LEFT);
    addIt(tabbedPane, "Tab One long title");
    addIt(tabbedPane, "Right"); //why is this title centered?
    addIt(tabbedPane, "Left");  //why is this title centered?
    f.add(tabbedPane);
    f.setSize(300, 200);
    f.setVisible(true);
  }
}