1 /* 2 $Id: NullObject.java,v 1.1 2006/06/13 22:15:02 galleon Exp $ 3 4 Copyright 2003 (C) James Strachan and Bob Mcwhirter. All Rights Reserved. 5 6 Redistribution and use of this software and associated documentation 7 ("Software"), with or without modification, are permitted provided 8 that the following conditions are met: 9 10 1. Redistributions of source code must retain copyright 11 statements and notices. Redistributions must also contain a 12 copy of this document. 13 14 2. Redistributions in binary form must reproduce the 15 above copyright notice, this list of conditions and the 16 following disclaimer in the documentation and/or other 17 materials provided with the distribution. 18 19 3. The name "groovy" must not be used to endorse or promote 20 products derived from this Software without prior written 21 permission of The Codehaus. For written permission, 22 please contact info@codehaus.org. 23 24 4. Products derived from this Software may not be called "groovy" 25 nor may "groovy" appear in their names without prior written 26 permission of The Codehaus. "groovy" is a registered 27 trademark of The Codehaus. 28 29 5. Due credit should be given to The Codehaus - 30 http://groovy.codehaus.org/ 31 32 THIS SOFTWARE IS PROVIDED BY THE CODEHAUS AND CONTRIBUTORS 33 ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT 34 NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 35 FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 36 THE CODEHAUS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 37 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 38 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 39 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 40 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 41 STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 42 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 43 OF THE POSSIBILITY OF SUCH DAMAGE. 44 45 */ 46 package org.codehaus.groovy.runtime; 47 48 import groovy.lang.GroovyObjectSupport; 49 50 public class NullObject extends GroovyObjectSupport { 51 private static NullObject ref; 52 53 /*** 54 * private constructor 55 **/ 56 private NullObject() { 57 } 58 59 /*** 60 * get the NullObject reference 61 **/ 62 public synchronized static NullObject getNullObject() { 63 if (ref == null) 64 ref = new NullObject(); 65 return ref; 66 } 67 68 /*** 69 * Since this is implemented as a singleton, we should avoid the 70 * use of the clone method 71 **/ 72 public Object clone() throws CloneNotSupportedException { 73 throw new CloneNotSupportedException(); 74 } 75 76 /*** 77 * @param property - the property to get 78 * @returns a NPE 79 **/ 80 public Object getProperty(String property) { 81 throw new NullPointerException("Cannot get property " + property + "() on null object"); 82 } 83 84 /*** 85 * @param property - the property to set 86 * @returns a NPE 87 **/ 88 public Object setProperty(String property) { 89 throw new NullPointerException("Cannot set property " + property + "() on null object"); 90 } 91 92 /*** 93 * @param - the name of the method to invoke 94 * @param args - arguments to the method 95 * @returns a NPE 96 * 97 **/ 98 public Object invokeMethod(String name, Object args) { 99 throw new NullPointerException("Cannot invoke method " + name + "() on null object"); 100 } 101 102 /*** 103 * @param to - the reference object with which to compare 104 * @returns - true if this object is the same as the to argument 105 **/ 106 public boolean equals(Object to) { 107 return to == null; 108 } 109 110 111 }