import java.awt.*;
     import java.util.*;

     // 維護一組按鈕,這樣在任意時刻只有一個被選中
     public class RadioButtonGroup extends Object
     {
          // 用來裝單選按鈕的動態可增長vector 
          protected Vector buttons;

          // 遍歷上述Vector的枚舉器
          protected Enumeration e;
          
          // 創建一個新的RadioButtonGroup對象
          public RadioButtonGroup()
          {
               buttons = new Vector();
          }

          // 將傳入的單選按鈕添加到vector中去
          public void add(RadioButton2D rb)
          {
               buttons.add(rb);
          }

          // 得到當前所選中的單選按鈕
          //如果沒有按鈕被選中的話則返回null
          public RadioButton2D getSelection()
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    RadioButton2D rb = (RadioButton2D)e.nextElement();

                    if(rb.isSelected())
                    {
                         return rb;
                    }
               }

               return null;
          }

          // 整組按鈕的可用/不可用狀態
          public void setEnabled(boolean b)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    ((RadioButton2D) e.nextElement()).setEnabled(b);
               }
          }

          // 設置整個按鈕組的可見性 
          public void setVisible(boolean v)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    ((RadioButton2D) e.nextElement()).setVisible(v);
               }
          }

          // 更新按鈕組,讓除了傳入的按鈕之外的按鈕設置為未選中狀態
          public void updateGroup(RadioButton2D rb)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    Object o = e.nextElement();
                    if(rb != o)
                    {
                         ((RadioButton2D) o).setSelected(false);
                    }
               }
          }

          // 繪制組中的每一個按鈕
          public void paint(Graphics2D g2d)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    ((RadioButton2D)e.nextElement()).paint(g2d);
               }
          }

          // 在給定的位置繪制組中的每一個按鈕
          public void paint(Graphics2D g2d, double dx, double dy)
          {
               for(e = buttons.elements(); e.hasMoreElements(); )
               {
                    ((RadioButton2D)e.nextElement()).paint(g2d, dx, dy);
               }
          }

     }    // RadioButtonGroup