package collation;

import java.util.*;
import javax.swing.*;

/**
   A combo box that lets users choose from among static field
   values whose names are given in the constructor.
   @version 1.15 2016-05-06
   @author Cay Horstmann
*/
public class EnumCombo<T> extends JComboBox<String>
{ 
   private Map<String, T> table = new TreeMap<>();

   /**
      Constructs an EnumCombo yielding values of type T.
      @param cl a class
      @param labels an array of strings describing static field names 
      of cl that have type T
   */
   public EnumCombo(Class<?> cl, String... labels)
   {  
      for (String label : labels)
      {  
         String name = label.toUpperCase().replace(' ', '_');
         try
         {  
            java.lang.reflect.Field f = cl.getField(name);
            @SuppressWarnings("unchecked") T value = (T) f.get(cl);
            table.put(label, value);
         }
         catch (Exception e)
         {  
            label = "(" + label + ")";
            table.put(label, null);
         }
         addItem(label);
      }
      setSelectedItem(labels[0]);
   }

   /**
      Returns the value of the field that the user selected.
      @return the static field value
   */
   public T getValue()
   {  
      return table.get(getSelectedItem());
   }
}