/** A class to represent two values.
 * @author Lew, 
 * snagged from http://groups.google.com/group/comp.lang.java.help/browse_thread/thread/f8b63fc645c1b487/1d94be050cfc249b
 * minimally touched up by Ian Barland.
 * @version 2008.Dec.06
 */
public class Pair <T, U> {
   private final T first;
   private final U second;
   private transient final int hash;

   /* @param f The first  value of this pair.
    * @param s The second value of this pair.
    */
   public Pair( T f, U s ) {
    this.first = f;
    this.second = s;
    hash = (first  == null? 0 : first.hashCode() * 31)
         + (second == null? 0 : second.hashCode());
   }

   /** Return The first  value of this pair.
    * @return The first  value of this pair.
    */
   public T getFirst()  { return first;  }
   
   /** Return The second value of this pair.
    * @return The second value of this pair.
    */
   public U getSecond() { return second; }

   @Override
   public int hashCode() { return hash; }

   @Override
   public boolean equals( Object oth ) {
    if ( this == oth ) {
      return true;
      }
    else if ( oth == null || !(this.getClass().isInstance( oth )) ) {
      return false;
      }
    else {
      Pair<T, U> other = getClass().cast( oth );  // This line will generate a 'unchecked type operation' warning.
      return (first  == null? other.first  == null : first.equals(  other.first  ))
          && (second == null? other.second == null : second.equals( other.second ));
      }
    }

  }