http://xml.apache.org/xalan-j/: Xalan-Java is an XSLT processor for transforming XML documents into HTML, text, or other XML document types. It implements XSL Transformations (XSLT) Version 1.0 and XML Path Language (XPath) Version 1.0 and can be used from the command line, in an applet or a servlet, or as a module in other program. (The Apache Software Foundation) 
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: XNull.java 468655 2006-10-28 07:12:06Z minchau $
 */
package org.apache.xpath.objects;

import org.apache.xml.dtm.DTM;
import org.apache.xpath.XPathContext;


This class represents an XPath null object, and is capable of
converting the null to other types, such as a string.

@xsl.usagegeneral
/**
 * This class represents an XPath null object, and is capable of
 * converting the null to other types, such as a string.
 * @xsl.usage general
 */
public class XNull extends XNodeSet
{
    static final long serialVersionUID = -6841683711458983005L;

  
Create an XObject.

/**
   * Create an XObject.
   */
  public XNull()
  {
    super();
  }

  
Tell what kind of class this is.

Returns:type CLASS_NULL
/**
   * Tell what kind of class this is.
   *
   * @return type CLASS_NULL
   */
  public int getType()
  {
    return CLASS_NULL;
  }

  
Given a request type, return the equivalent string.
For diagnostic purposes.

Returns:type string "#CLASS_NULL"
/**
   * Given a request type, return the equivalent string.
   * For diagnostic purposes.
   *
   * @return type string "#CLASS_NULL"
   */
  public String getTypeString()
  {
    return "#CLASS_NULL";
  }

  
Cast result object to a number.

Returns:0.0
/**
   * Cast result object to a number.
   * 
   * @return 0.0
   */

  public double num()
  {
    return 0.0;
  }

  
Cast result object to a boolean.

Returns:false
/**
   * Cast result object to a boolean.
   *
   * @return false
   */
  public boolean bool()
  {
    return false;
  }

  
Cast result object to a string.

Returns:empty string ""
/**
   * Cast result object to a string.
   *
   * @return empty string ""
   */
  public String str()
  {
    return "";
  }

  
Cast result object to a result tree fragment.

Params:
  • support – XPath context to use for the conversion
Returns:The object as a result tree fragment.
/**
   * Cast result object to a result tree fragment.
   *
   * @param support XPath context to use for the conversion
   *
   * @return The object as a result tree fragment.
   */
  public int rtf(XPathContext support)
  {
    // DTM frag = support.createDocumentFragment();
    // %REVIEW%
    return DTM.NULL;
  }

//  /**
//   * Cast result object to a nodelist.
//   *
//   * @return null
//   */
//  public DTMIterator iter()
//  {
//    return null;
//  }

  
Tell if two objects are functionally equal.

Params:
  • obj2 – Object to compare this to
Returns:True if the given object is of type CLASS_NULL
/**
   * Tell if two objects are functionally equal.
   *
   * @param obj2 Object to compare this to
   *
   * @return True if the given object is of type CLASS_NULL
   */
  public boolean equals(XObject obj2)
  {
    return obj2.getType() == CLASS_NULL;
  }
}