I'm currently struggling to understand why I would need to use a HistoricMapEntry (better name?). It has a part in the undo events code you wrote I believe, but outside that where does it fit and what use is it? Use cases please :-)
Stephen ----- Original Message ----- From: "Neil O'Toole" <[EMAIL PROTECTED]> > > 'Record' confused me and made me think of databases. Is > > KeyValueHistory a better name? > > Stephen, you're probably right. I had been bouncing back and forth > between 'Record' and 'History'... the data structure does *record* a > kv-pair's *history*, but in fact only the most recent part (one state > transition 'record') of the history. > > However, one would expect that a "KeyValueHistory" class should be able > to store the entire history of a key (as well as just a single value). > I hadn't initially needed this capability for my own purposes, but I > now see the usefulness. So, > > #getPreviousValue : Object > > should probably be replaced with: > > #getAllValues : List > > What do we think? In terms of design, either the constructors would get > very messy to use, or we need to add factory methods to distinguish > between: > > KeyValueHistory( Object key, Object value) > KeyValueHistory( Object key, List values) > > Attached is an implementation that supports multiple previous values, > and provides static factory methods. Thoughts? > > - Neil > > > ---------------------------------------------------------------------------- ---- > /* > * $Header: x:/apps/cvsnt/cvs_repository/main/notifyingcollections/src/java/org/apache/c ommons/collections/KeyValueRecord.java,v 1.2 2003/09/20 22:00:32 otoolen 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 acknowledgment: > * "This product includes software developed by the > * Apache Software Foundation (http://www.apache.org/)." > * Alternately, this acknowledgment may appear in the software itself, > * if and wherever such third-party acknowledgments 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; > > import java.util.ArrayList; > import java.util.Collections; > import java.util.List; > import java.util.Map; > > /** > * An immutable {key, value, previous-value} triplet. This class is frequently used > * in conjunction with <code>Map.Entry</code>. A constructor is provided to create > * a <code>KeyValueRecord</code> from a <code>Map.Entry</code>, and the [EMAIL PROTECTED] #asMapEntry} > * method can be used to view an object of this class as a <code>Map.Entry</code>. > * Note that it is not possible for <code>KeyValueRecord</code> to implement the <code>Map.Entry</code> > * interface as the <code>#equals</code> implementations are not compatible. > * > * > * > * @author Neil O'Toole > */ > > public class KeyValueHistory > { > > /** > * Create a new <code>KeyValueHistory</code> with supplied key and value, > * and no previous values. > */ > public static KeyValueHistory createFromKeyValue(final Object key, final Object value) > { > return new KeyValueHistory(key, Collections.singletonList(value)); > } > > > /** > * Create a new <code>KeyValueHistory</code> with the specified key and values. > * The supplied list must: > * <ul> > * <li>contain at least one value</li> > * <li>contain the values in reverse-chronological order (i.e. most > * recent value first)</li> > * <li>be immutable</li> > * </ul> > * > * @param values an immutable list of the values associated with this key. > * @throws IllegalArgumentException if <code>values</code> is <code>null</code> or > * is empty. <br />Note: If the value associated with the key is the value <code>null</code>, > * then supply <code>Collections#singletonList( null )</code>. > */ > public static KeyValueHistory createFromKeyValueList(final Object key, final List values) > { > if (values == null || values.size() < 1) > { > throw new IllegalArgumentException("The supplied 'values' list must contain at least one value."); > } > > return new KeyValueHistory(key, values); > } > > /** > * Create a new <code>KeyValueHistory</code> with supplied key, value > * and previous value. > */ > public static KeyValueHistory createFromKeyValuePrevious(final Object key, final Object value, final Object previous) > { > final List values = new ArrayList(2); > values.add(value); > values.add(previous); > > return new KeyValueHistory(key, Collections.unmodifiableList(values)); > } > /** > * Create a new <code>KeyValueHistory</code> with key and value from the supplied > * <code>Map.Entry</code> and no previous value. > */ > public static KeyValueHistory createFromMapEntry(final Map.Entry entry) > { > return new KeyValueHistory(entry.getKey(), Collections.singletonList(entry.getValue())); > } > > private int hash = -1; // lazily calculated > > private final Object key; > private final List values; > > > > > /** > * Create a new <code>KeyValueHistory</code> with the specified key and values. > * The supplied list: > * <ul> > * <li>must contain at least one value</li> > * <li>must contain the values in reverse-chronological order (i.e. most > * recent value first)</li> > * <li>must be immutable</li> > * > * @param values an immutable List of the values associated with this key. > */ > protected KeyValueHistory(final Object key, final List values) > { > this.key = key; > this.values = values; > } > > /** > * Returns a [EMAIL PROTECTED] Map.Entry} view of the supplied <code>KeyValueRecord</code>. The > * returned entry is unmodifiable (<code>#setValue</code> throws an [EMAIL PROTECTED] UnsupportedOperationException}), > * as the backing <code>KeyValueRecord</code> is itself immutable. > * The returned entry correctly implements the <code>#hashCode</code> and > * <code>#equals</code> operations as per the <code>Map.Entry</code> contract. > */ > > public Map.Entry asMapEntry() > { > return new Map.Entry() > { > private int hash = -1; > > public boolean equals(Object o) > { > if (o instanceof Map.Entry == false) > { > return false; > } > > if (o == this) > { > return true; > } > > Map.Entry e = (Map.Entry) o; > > return ( > KeyValueHistory.this.getKey() == null > ? e.getKey() == null > : KeyValueHistory.this.getKey().equals(e.getKey())) > && (KeyValueHistory.this.getValue() == null > ? e.getValue() == null > : KeyValueHistory.this.getValue().equals(e.getValue())); > } > > public Object getKey() > { > return KeyValueHistory.this.getKey(); > } > > public Object getValue() > { > return KeyValueHistory.this.getValue(); > } > > public int hashCode() > { > if (this.hash == -1) > { > this.hash = > (KeyValueHistory.this.getKey() == null ? 0 : KeyValueHistory.this.getKey().hashCode()) > ^ (KeyValueHistory.this.getValue() == null ? 0 : KeyValueHistory.this.getValue().hashCode()); > } > > return this.hash; > } > > public Object setValue(Object value) > { > throw new UnsupportedOperationException("This Map.Entry is unmodifiable."); > } > > public String toString() > { > return new StringBuffer() > .append(KeyValueHistory.this.getKey()) > .append('=') > .append(KeyValueHistory.this.getValue()) > .toString(); > } > }; > > } > > /** > * Compares the specified object with this <code>KeyValueRecord</code> for equality. Returns > * true if the given object is also a <code>KeyValueRecord</code> and > * the records' key, value, and previous value are equal. > * > * @param o object to be compared for equality with this <code>KeyValueRecord</code>. > * @return <code>true</code> if the specified object is equal to this > * record. > */ > public boolean equals(final Object o) > { > if (!(o instanceof KeyValueHistory)) > { > return false; > } > > if (this == o) > { > return true; > } > > final KeyValueHistory kvr = (KeyValueHistory) o; > > return (this.key == null ? kvr.key == null : this.key.equals(kvr.key)) > && this.values.equals(kvr.values); > } > > /** > * Returns the first value previously associated with this key, if any. Note that > * <code>null</code> will be returned > * if the previous value is <code>null</code> <i>or</i> if there are no previous values > * Therefore [EMAIL PROTECTED] #hasPreviousValues()} should be used to test if there is a previous value. > * > * @return the previous value (which may be <code>null</code>) > * associated with this record's key, or <code>null</code> if there is no > * previous value. > */ > /* > public Object getPreviousValue() > { > return (this.values.size() < 2) ? null : this.values.get(1); > }*/ > > /* > public List getAllPreviousValues() > { > return this.values.subList(1, values.size() -1); > } > */ > > /** > * Return all values associated with this key, in reverse chronological > * order. The most recent (current) value is at index zero, the previous value is > * at index one, the value previous to that at index two, etc.. If there are no > * previous values associated with this key, then list will contain only one element (the current value). > * The returned list is immutable. > * > * @return an immutable list of the values associated with this key, the list having a minimum size of one. > */ > public List getAllValues() > { > return this.values; > } > > /** > * Returns the key associated with this record. > */ > public Object getKey() > { > return this.key; > } > > /** > * Returns the current (or most recent) value associated with this record's key. > * > * @return the value (which may be <code>null</code>) > * associated with this record's key > */ > public Object getValue() > { > return this.values.get(0); > } > > public int hashCode() > { > if (this.hash == -1) > { > this.hash = > (this.key == null ? 0 : this.key.hashCode()) > ^ this.values.hashCode(); > } > > return this.hash; > } > > /** > * Returns true if this record's key > * was associated with a value previous to being > * associated with its current value. > * > * @return <code>true</code> if this key previously had a value associated > * with it, <code>false</code> otherwise. > * @see #getPreviousValue() > */ > public boolean hasPreviousValues() > { > return this.values.size() > 1; > } > > /** > * Returns a string representation of this <code>KeyValueHistory</code>. > * > */ > public String toString() > { > final StringBuffer sb = new StringBuffer().append(this.key).append('=').append(this.values); > > return sb.toString(); > } > > } > ---------------------------------------------------------------------------- ---- > /* > * $Header: x:/apps/cvsnt/cvs_repository/main/notifyingcollections/src/test/org/apache/c ommons/collections/TestKeyValueHistory.java,v 1.1 2003/09/20 22:00:46 otoolen 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 acknowledgment: > * "This product includes software developed by the > * Apache Software Foundation (http://www.apache.org/)." > * Alternately, this acknowledgment may appear in the software itself, > * if and wherever such third-party acknowledgments 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; > > import java.util.HashMap; > import java.util.Map; > > import junit.framework.TestCase; > > > /** > * > * @author Neil O'Toole > */ > public class TestKeyValueHistory extends TestCase > { > private final String key = "key"; > private final String value = "value"; > private final String previous = "previous"; > > public TestKeyValueHistory(String testName) > { > super(testName); > > } > > public static void main(String[] args) > { > junit.textui.TestRunner.run(TestKeyValueHistory.class); > } > > public void testKeyValueHistory() > { > > // KVR with no previous value > KeyValueHistory kvr = KeyValueHistory.createFromKeyValue(key, value); > > assertTrue( > kvr.getKey() == key > && kvr.getValue() == value > && kvr.hasPreviousValues() == false); > > assertTrue(kvr.equals(kvr)); > assertTrue(kvr.toString().equals("key=[value]")); > > // KVR with a previous value > KeyValueHistory kvr2 = KeyValueHistory.createFromKeyValuePrevious(key, value, previous); > > assertTrue( > kvr2.getKey() == key > && kvr2.getValue() == value > && kvr2.hasPreviousValues() == true > && kvr2.getAllValues().get(1) == previous); > > assertTrue(kvr2.equals(kvr2)); > assertTrue(kvr2.toString().equals("key=[value, previous]")); > > assertFalse(kvr.equals(kvr2)); > assertFalse(kvr.hashCode() == kvr2.hashCode()); > > // test that a previous value of 'null' is treated differently to no previous value > KeyValueHistory kvr3 = KeyValueHistory.createFromKeyValuePrevious(key, value, null); > assertTrue(kvr3.equals(kvr3)); > assertTrue(kvr3.toString().equals("key=[value, null]")); > assertFalse(kvr3.equals(kvr)); > assertFalse(kvr3.equals(kvr2)); > > assertFalse(kvr3.hashCode() == kvr2.hashCode()); > assertFalse(kvr3.hashCode() == kvr.hashCode()); > > // test the Map.Entry handling > Map map = new HashMap(); > map.put(key, value); > > Map.Entry entry = (Map.Entry) map.entrySet().iterator().next(); > > KeyValueHistory kvr4 = KeyValueHistory.createFromMapEntry(entry); > > assertTrue( > kvr4.getKey() == key > && kvr4.getValue() == value > && kvr4.hasPreviousValues() == false); > > assertTrue(kvr4.equals(kvr4)); > assertTrue(kvr4.equals(kvr)); > assertTrue(kvr4.toString().equals("key=[value]")); > > assertFalse("Map.Entry and KeyValueHistory are never equal", kvr4.equals(entry)); > > Map.Entry entry2 = kvr4.asMapEntry(); > > assertTrue(entry.equals(entry2)); > assertTrue(entry.hashCode() == entry2.hashCode()); > > } > > } > > ---------------------------------------------------------------------------- ---- > --------------------------------------------------------------------- > 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]
