skierinfo.java

Java程序设计高级教程（第三版）

package com.nearhills;

import java.util.*;

public class SkierInfo {
   private int id;
   private Vector trips;
   private int numTrips;

   public SkierInfo( ) {
     id = 0; 
   }
  
   public void setId( int id ) {
      if ( this.id != id ) {
         trips = null; 
      }
      this.id = id;
   }

   public int getNumTrips( ) {
      countTrips();
      return numTrips;
   }     

   public int countTrips( ) {
      if ( id < 1) { 
         numTrips = 0;
         trips = null;   
      } else if ( trips == null ) {
         trips = SkiTrip.getTrips( id );
         numTrips = trips == null ? 0 : trips.size() ;
      }
      return numTrips;
   } 

   public String getTripList( ) {
      if ( countTrips() == 0 ) {
         return "";
      }
      String list = "";
      Enumeration e = trips.elements();
 	 while( e.hasMoreElements() ) {
            list += e.nextElement().toString() + "\n";
         }
      return list;
   }
}