import org.xml.sax.*;
import org.xml.sax.helpers.*;
import java.util.StringTokenizer;
import javax.swing.*;

/** A SAX parser handler that keeps track of the number
 *  of copies of Core Web Programming ordered. Entries
 *  that look like this will be recorded:
 *  <XMP>
 *    ...
 *    <count>23</count>
 *    <book>
 *      <isbn>0130897930</isbn>
 *      ...
 *    </book>
 *  </XMP>
 *  All other entries will be ignored -- different books,
 *  orders for yachts, things that are not even orders, etc.
 *
 *  Taken from Core Web Programming from 
 *  Prentice Hall and Sun Microsystems Press,
 *  http://www.corewebprogramming.com/.
 *  &copy; 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted. 
 */

public class CountHandler extends DefaultHandler {
  private boolean collectCount = false;
  private boolean collectISBN = false;
  private int currentCount = 0;
  private int totalCount = 0;

  /** If you start the "count" or "isbn" elements,
   *  set a flag so that the characters method can check
   *  the value of the tag body.
   */
  
  public void startElement(String namespaceUri,
                           String localName,
                           String qualifiedName,
                           Attributes attributes)
      throws SAXException {
    if (qualifiedName.equals("count")) {
      collectCount = true;
      currentCount = 0;
    } else if (qualifiedName.equals("isbn")) {
      collectISBN = true;
    }
  }

  /** If you end the "count" or "isbn" elements,
   *  set a flag so that the characters method will no
   *  longer check the value of the tag body.
   */

  public void endElement(String namespaceUri,
                         String localName,
                         String qualifiedName)
      throws SAXException {
    if (qualifiedName.equals("count")) {
      collectCount = false;
    } else if (qualifiedName.equals("isbn")) {
      collectISBN = false;
    }
  }

  /** Since the "count" entry comes before the "book"
   *  entry (which contains "isbn"), we have to temporarily
   *  record all counts we see. Later, if we find a
   *  matching "isbn" entry, we will record that temporary
   *  count.
   */

  public void characters(char[] chars,
                         int startIndex,
                         int length) {
    if (collectCount || collectISBN) {
      String dataString =
        new String(chars, startIndex, length).trim();
      if (collectCount) {
        try {
          currentCount = Integer.parseInt(dataString);
        } catch(NumberFormatException nfe) {
          System.err.println("Ignoring malformed count: " +
                             dataString);
        }
      } else if (collectISBN) {
        if (dataString.equals("0130897930")) {
          totalCount = totalCount + currentCount;
        }
      }
    }
  }

  /** Report the total number of copies ordered.
   *  Gently chide underachievers.
   */
  
  public void endDocument() throws SAXException {
    String message =
      "You ordered " + totalCount + " copies of \n" +
      "Core Web Programming Second Edition.\n";
    if (totalCount < 250) {
      message = message + "Please order more next time!";
    } else {
      message = message + "Thanks for your order.";
    }
  JOptionPane.showMessageDialog(null, message);
  }
}