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]
