Java by API/javax.swing/ComboBoxModel

extends AbstractListModel implements ComboBoxModel

import java.awt.BorderLayout;
import java.util.ArrayList;
import java.util.Collection;
import javax.swing.AbstractListModel;
import javax.swing.ruboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
public class MainClass {
  public static void main(String args[]) {
    JFrame frame = new JFrame("ArrayListComboBoxModel");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Collection<Object> col = System.getProperties().values();
    ArrayList<Object> arrayList = new ArrayList<Object>(col);
    ArrayListComboBoxModel model = new ArrayListComboBoxModel(arrayList);
    JComboBox comboBox = new JComboBox(model);
    frame.add(comboBox, BorderLayout.NORTH);
    frame.setSize(300, 225);
    frame.setVisible(true);
  }
}
class ArrayListComboBoxModel extends AbstractListModel implements ComboBoxModel {
  private Object selectedItem;
  private ArrayList anArrayList;
  public ArrayListComboBoxModel(ArrayList arrayList) {
    anArrayList = arrayList;
  }
  public Object getSelectedItem() {
    return selectedItem;
  }
  public void setSelectedItem(Object newValue) {
    selectedItem = newValue;
  }
  public int getSize() {
    return anArrayList.size();
  }
  public Object getElementAt(int i) {
    return anArrayList.get(i);
  }
}