1 /* 2 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/CountFunction.java,v 1.14 2006/02/05 21:47:41 elharo Exp $ 3 * $Revision: 1.14 $ 4 * $Date: 2006/02/05 21:47:41 $ 5 * 6 * ==================================================================== 7 * 8 * Copyright 2000-2002 bob mcwhirter & James Strachan. 9 * All rights reserved. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions are 13 * met: 14 * 15 * * Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 18 * * Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 22 * * Neither the name of the Jaxen Project nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 27 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 29 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER 30 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 31 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 32 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 33 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 34 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 35 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 36 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37 * 38 * ==================================================================== 39 * This software consists of voluntary contributions made by many 40 * individuals on behalf of the Jaxen Project and was originally 41 * created by bob mcwhirter <bob@werken.com> and 42 * James Strachan <jstrachan@apache.org>. For more information on the 43 * Jaxen Project, please see <http://www.jaxen.org/>. 44 * 45 * $Id: CountFunction.java,v 1.14 2006/02/05 21:47:41 elharo Exp $ 46 */ 47 48 package org.jaxen.function; 49 50 import java.util.List; 51 52 import org.jaxen.Context; 53 import org.jaxen.Function; 54 import org.jaxen.FunctionCallException; 55 56 /*** 57 * <p><b>4.1</b> <code><i>number</i> count(<i>node-set</i>)</code></p> 58 * 59 * <blockquote src="http://www.w3.org/TR/xpath#function-count"> 60 * The <b>count</b> function returns the number of nodes in the argument node-set. 61 * </blockquote> 62 * @author bob mcwhirter (bob @ werken.com) 63 * @see <a href="http://www.w3.org/TR/xpath#function-count">Section 4.1 of the XPath Specification</a> 64 */ 65 public class CountFunction implements Function 66 { 67 68 /*** 69 * Create a new <code>CountFunction</code> object. 70 */ 71 public CountFunction() {} 72 73 /*** 74 * <p> 75 * Returns the number of nodes in the specified node-set. 76 * </p> 77 * @param context ignored 78 * @param args the function arguments 79 * 80 * @return a <code>Double</code> giving the integral number of items in the first argument 81 * 82 * @throws FunctionCallException if args does not have exactly one 83 * item; or that item is not a <code>List</code> 84 */ 85 public Object call(Context context, 86 List args) throws FunctionCallException 87 { 88 if (args.size() == 1) 89 { 90 return evaluate( args.get(0) ); 91 } 92 93 throw new FunctionCallException( "count() requires one argument." ); 94 } 95 96 /*** 97 * <p> 98 * Returns the number of nodes in the specified node-set. 99 * </p> 100 * 101 * @param obj a <code>List</code> of nodes 102 * @return the integral number of items in the list 103 * @throws FunctionCallException if obj is not a <code>List</code> 104 */ 105 public static Double evaluate(Object obj) throws FunctionCallException 106 { 107 108 if (obj instanceof List) 109 { 110 return new Double( ((List) obj).size() ); 111 } 112 113 throw new FunctionCallException("count() function can only be used for node-sets"); 114 115 } 116 117 }