I believe that the test case for DefaultMapEntry will test by extension test KeyValuePair??.. though we can simply subclass the test case also - should we do this?
N. --- Stephen Colebourne <[EMAIL PROTECTED]> wrote: > I'm happy to add it....with a test case :-) > Stephen > > ----- Original Message ----- > From: "Neil O'Toole" <[EMAIL PROTECTED]> > > > My suggested solution is to add a class "KeyValue.java" > containing > > > the code from DefaultMapEntry, but not implementing Map.Entry. > > > DefaultMapEntry can then subclass KeyValue and implement > Map.Entry, > > > and be declared final. > > > > Suggested solution attached (KeyValuePair.java and patch for > > DefaultMapEntry.java). Note that: > > > > - The superflous null check is removed from DefaultMapEntry#equals > > (instanceof checks for null). > > - The DefaultMapEntry #equals and #hashCode methods are declared > final. > > The 'correct' approach is probably that the whole class should be > > declared final - thoughts on this??. > > - KeyValuePair has a toString() method. > > > > Unless there are objections, anyone want to add this to CVS? > > > > Neil > > > > > > --- Neil O'Toole <[EMAIL PROTECTED]> wrote: > > > > > ** I had a swift look through [collections] and [lang], and > > > didn't > > > > see > > > > > a simple KeyValuePair implementation... Have I missed this > > > > somewhere? > > > > > > > > DefaultMapEntry IIRC is the simple Map.Entry impl. > > > > Stephen > > > > > > > > > > Although one (including my good self!) might initially think that > a > > > key-value class and a Map.Entry class are interchangeable, this > is > > > not > > > in fact the case. DefaultMapEntry is not suitable for use as a > > > general > > > purpose KeyValue class, as it is effectively non-extendable (and > > > there > > > are many cases where it is useful to extend a KeyValue class). In > > > fact, > > > DefaultMapEntry (or at the very least its #equals and #hashcode > > > methods) should be declared final so that users won't make the > > > mistake > > > of subclassing it. > > > > > > DefaultMapEntry is not extendable because the #equals method is > > > contractually specified by Map.Entry to only evalute the members > of > > > Map.Entry. A non-trivial subclass of DefaultMapEntry will add > members > > > that will be used in #equals comparision. To make use of these > > > members > > > in #equals will of course violate the Map.Entry#equals contract. > > > > > > This non-extensibility property applies to any class that > inherits or > > > implements an #equals method with a similar closed #equals > contract, > > > and any such class should be declared final to prevent accidental > > > subclassing (or again, at the very least the #hashcode and > #equals > > > methods should be declared final, though the user might just > ignore > > > those methods, resulting in unfortunate code). > > > > > > My suggested solution is to add a class "KeyValue.java" > containing > > > the > > > code from DefaultMapEntry, but not implementing Map.Entry. > > > DefaultMapEntry can then subclass KeyValue and implement > Map.Entry, > > > and > > > be declared final. > > > > > > - Neil > > > > > > > > > > > > > --------------------------------------------------------------------- > > > To unsubscribe, e-mail: > [EMAIL PROTECTED] > > > For additional commands, e-mail: > [EMAIL PROTECTED] > > > > > > > > ---------------------------------------------------------------------------- > ---- > > > > /* > > * $Header: > /home/cvspublic/jakarta-commons/collections/src/java/org/apache/commons/coll > ections/DefaultMapEntry.java,v 1.11 2003/08/31 17:26:43 scolebourne > Exp $ > > * > ==================================================================== > > * > > * The Apache Software License, Version 1.1 > > * > > * Copyright (c) 2001-2003 The Apache Software Foundation. All > rights > > * reserved. > > * > > * Redistribution and use in source and binary forms, with or > without > > * modification, are permitted provided that the following > conditions > > * are met: > > * > > * 1. Redistributions of source code must retain the above > copyright > > * notice, this list of conditions and the following disclaimer. > > * > > * 2. Redistributions in binary form must reproduce the above > copyright > > * notice, this list of conditions and the following disclaimer > in > > * the documentation and/or other materials provided with the > > * distribution. > > * > > * 3. The end-user documentation included with the redistribution, > if > > * any, must include the following acknowledgement: > > * "This product includes software developed by the > > * Apache Software Foundation (http://www.apache.org/)." > > * Alternately, this acknowledgement may appear in the software > itself, > > * if and wherever such third-party acknowledgements normally > appear. > > * > > * 4. The names "The Jakarta Project", "Commons", and "Apache > Software > > * Foundation" must not be used to endorse or promote products > derived > > * from this software without prior written permission. For > written > > * permission, please contact [EMAIL PROTECTED] > > * > > * 5. Products derived from this software may not be called > "Apache" > > * nor may "Apache" appear in their names without prior written > > * permission of the Apache Software Foundation. > > * > > * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED > > * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED > WARRANTIES > > * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE > > * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR > > * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, > > * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT > > * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF > > * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED > AND > > * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT > LIABILITY, > > * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY > OUT > > * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY > OF > > * SUCH DAMAGE. > > * > ==================================================================== > > * > > * This software consists of voluntary contributions made by many > > * individuals on behalf of the Apache Software Foundation. For > more > > * information on the Apache Software Foundation, please see > > * <http://www.apache.org/>. > > * > > */ > > package org.apache.commons.collections; > > > > > > > > /** > > * A simple key-value pair. > > * > > * @since Commons Collections 3.0 > > * @version $Revision: $ > > * > > * @author <a href="mailto:[EMAIL PROTECTED]">James Strachan</a> > > * @author <a href="mailto:[EMAIL PROTECTED]">Michael A. Smith</a> > > * @author Neil O'Toole > > */ > > public class KeyValuePair{ > > > > /** The key */ > > private Object key; > > /** The value */ > > private Object value; > > > > /** > > * Constructs a new <Code>DefaultMapEntry</Code> with a null > key > > * and null value. > > */ > > public KeyValuePair() { > > } > > > > /** > > * Constructs a new <Code>DefaultMapEntry</Code> with the given > > * key and given value. > > * > > * @param key the key for the entry, may be null > > * @param value the value for the entry, may be null > > */ > > public KeyValuePair(Object key, Object value) { > > this.key = key; > > this.value = value; > > } > > > > > > /** > > * Returns true if the compared object is also a > <code>KeyValuePair</code>, > > * and its key and value are equal to this object's key and value. > > */ > > public boolean equals(Object o) { > > > > if ( o == this ) return true; > > > > if ( o instanceof KeyValuePair == false ) return false; > > > > KeyValuePair e2 = (KeyValuePair) o; > > return ((getKey() == null ? > > e2.getKey() == null : > getKey().equals(e2.getKey())) && > > (getValue() == null ? > > e2.getValue() == null : > getValue().equals(e2.getValue()))); > > } > > > > > > > > public int hashCode() { > > return ( ( getKey() == null ? 0 : getKey().hashCode() ) ^ > > ( getValue() == null ? 0 : getValue().hashCode() ) > ); > > } > > > > > > > > /** > > * Returns the key. > > * > > * @return the key > > */ > > public Object getKey() { > > return key; > > } > > > > /** > > * Returns the value. > > * > > * @return the value > > */ > > public Object getValue() { > > return value; > > } > > > > > > > > /** > > * Sets the key. > > * > > * @param key the new key > > */ > > public void setKey(Object key) { > > this.key = key; > > } > > > > /** > > * Sets the value. > > * > > * @return the old value of the value > > * @param value the new value > > */ > > public Object setValue(Object value) { > > Object answer = this.value; > > this.value = value; > > return answer; > > } > > > > public String toString() > > { > > return new > StringBuffer().append(getKey()).append('=').append(getValue()).toString(); > > } > > } > > > > > ---------------------------------------------------------------------------- > ---- > > > > Index: DefaultMapEntry.java > > =================================================================== > > RCS file: > /home/cvspublic/jakarta-commons/collections/src/java/org/apache/commons/coll > ections/DefaultMapEntry.java,v > > retrieving revision 1.11 > > diff -u -r1.11 DefaultMapEntry.java > > --- DefaultMapEntry.java 31 Aug 2003 17:26:43 -0000 1.11 > > +++ DefaultMapEntry.java 23 Sep 2003 02:00:14 -0000 > > @@ -67,13 +67,10 @@ > > * > > * @author <a href="mailto:[EMAIL PROTECTED]">James > Strachan</a> > > * @author <a href="mailto:[EMAIL PROTECTED]">Michael A. Smith</a> > > + * @author Neil O'Toole > > */ > > -public class DefaultMapEntry implements Map.Entry { > > +public class DefaultMapEntry extends KeyValuePair implements > Map.Entry { > > > > - /** The key */ > > - private Object key; > > - /** The value */ > > - private Object value; > > > > /** > > * Constructs a new <Code>DefaultMapEntry</Code> with a null > key > > @@ -90,20 +87,18 @@ > > * @param value the value for the entry, may be null > > */ > > public DefaultMapEntry(Object key, Object value) { > > - this.key = key; > > - this.value = value; > > + super(key, value); > > } > > > > /** > > * Implemented per API documentation of > > * [EMAIL PROTECTED] java.util.Map.Entry#equals(Object)} > > */ > > - public boolean equals(Object o) { > > - if( o == null ) return false; > > + public final boolean equals(Object o) { > > if( o == this ) return true; > > > > - if ( ! (o instanceof Map.Entry ) ) > > - return false; > > + if ( !(o instanceof Map.Entry ) ) return false; > > + > > Map.Entry e2 = (Map.Entry)o; > > return ((getKey() == null ? > > e2.getKey() == null : > getKey().equals(e2.getKey())) && > > @@ -116,57 +111,12 @@ > > * Implemented per API documentation of > > * [EMAIL PROTECTED] java.util.Map.Entry#hashCode()} > > */ > > - public int hashCode() { > > + public final int hashCode() { > > return ( ( getKey() == null ? 0 : getKey().hashCode() ) ^ > > ( getValue() == null ? 0 : getValue().hashCode() > ) ); > > } > > > > > > > > - // Map.Entry interface > > - > //------------------------------------------------------------------------- > > - > > - /** > > - * Returns the key. > > - * > > - * @return the key > > - */ > > - public Object getKey() { > > - return key; > > - } > > - > > - /** > > - * Returns the value. > > - * > > - * @return the value > > - */ > > - public Object getValue() { > > - return value; > > - } > > - > > - // Properties > > - > //------------------------------------------------------------------------- > > - > > - /** > > - * Sets the key. This method does not modify any map. > > - * > > - * @param key the new key > > - */ > > - public void setKey(Object key) { > > - this.key = key; > > - } > > - > > - /** > > - * Note that this method only sets the local reference inside > this > object and > > - * does not modify the original Map. > > - * > > - * @return the old value of the value > > - * @param value the new value > > - */ > > - public Object setValue(Object value) { > > - Object answer = this.value; > > - this.value = value; > > - return answer; > > - } > > > > } > > > > > > > ---------------------------------------------------------------------------- > ---- > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: [EMAIL PROTECTED] > > For additional commands, e-mail: > [EMAIL PROTECTED] > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
