Swing Components Java

// Example from http://www.crionics.com/products/opensource/faq/swing_ex/SwingExamples.html
/* (swing1.1) */
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Rectangle;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Vector;
import javax.swing.ComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.plaf.basic.BasicComboPopup;
import javax.swing.plaf.basic.ComboPopup;
import javax.swing.plaf.metal.MetalComboBoxUI;
/**
 * @version 1.0 12/12/98
 */
public class SteppedComboBoxExample extends JFrame {
  public SteppedComboBoxExample() {
    super("SteppedComboBox Example");
    String[] str = { "A", "abcdefghijklmnopqrstuvwxyz",
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "0123456789" };
    SteppedComboBox combo = new SteppedComboBox(str);
    Dimension d = combo.getPreferredSize();
    combo.setPreferredSize(new Dimension(50, d.height));
    combo.setPopupWidth(d.width);
    getContentPane().setLayout(new FlowLayout());
    getContentPane().add(combo);
  }
  public static void main(String args[]) {
    try {
        UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
    } catch (Exception evt) {}
  
    SteppedComboBoxExample f = new SteppedComboBoxExample();
    f.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
    f.setSize(300, 100);
    f.show();
  }
}
class SteppedComboBoxUI extends MetalComboBoxUI {
  protected ComboPopup createPopup() {
    BasicComboPopup popup = new BasicComboPopup(comboBox) {
      public void show() {
        Dimension popupSize = ((SteppedComboBox) comboBox)
            .getPopupSize();
        popupSize
            .setSize(popupSize.width,
                getPopupHeightForRowCount(comboBox
                    .getMaximumRowCount()));
        Rectangle popupBounds = computePopupBounds(0, comboBox
            .getBounds().height, popupSize.width, popupSize.height);
        scroller.setMaximumSize(popupBounds.getSize());
        scroller.setPreferredSize(popupBounds.getSize());
        scroller.setMinimumSize(popupBounds.getSize());
        list.invalidate();
        int selectedIndex = comboBox.getSelectedIndex();
        if (selectedIndex == -1) {
          list.clearSelection();
        } else {
          list.setSelectedIndex(selectedIndex);
        }
        list.ensureIndexIsVisible(list.getSelectedIndex());
        setLightWeightPopupEnabled(comboBox.isLightWeightPopupEnabled());
        show(comboBox, popupBounds.x, popupBounds.y);
      }
    };
    popup.getAccessibleContext().setAccessibleParent(comboBox);
    return popup;
  }
}
class SteppedComboBox extends JComboBox {
  protected int popupWidth;
  public SteppedComboBox(ComboBoxModel aModel) {
    super(aModel);
    setUI(new SteppedComboBoxUI());
    popupWidth = 0;
  }
  public SteppedComboBox(final Object[] items) {
    super(items);
    setUI(new SteppedComboBoxUI());
    popupWidth = 0;
  }
  public SteppedComboBox(Vector items) {
    super(items);
    setUI(new SteppedComboBoxUI());
    popupWidth = 0;
  }
  public void setPopupWidth(int width) {
    popupWidth = width;
  }
  public Dimension getPopupSize() {
    Dimension size = getSize();
    if (popupWidth < 1)
      popupWidth = size.width;
    return new Dimension(popupWidth, size.height);
  }
}