2004-02-19 16:41:04 -05:00
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2006-11-29 02:41:17 -05:00
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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2004-02-19 16:41:04 -05:00
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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-->
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2002-06-28 23:49:01 -04:00
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<html>
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<head>
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2007-07-31 00:17:09 -04:00
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<title>Developers guide for Apache Commons "Collections" Package</title>
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</head>
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2002-06-28 23:49:01 -04:00
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<body bgcolor="white">
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<div align="center">
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2007-07-31 00:17:09 -04:00
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<h1>The Apache Commons <em>Collections</em> Package</h1>
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2002-06-28 23:49:01 -04:00
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<h2>Developers Guide</h2>
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<a href="#Introduction">[Introduction]</a>
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<a href="#CollectionInterfaces">[Collection Interfaces]</a>
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<a href="#CollectionImplementations">[Collection Implementations]</a>
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<a href="#UtilityClasses">[Utility Classes]</a>
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<a href="#CodingStandards">[Coding Standards]</a>
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<br />
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<br />
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2002-06-28 23:49:01 -04:00
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</div>
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<a name="Introduction"></a>
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<h3>1. INTRODUCTION</h3>
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<p>The <em>Collections</em> package contains a set of Java classes that extend
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or augment the Java Collections Framework. This developers guide seeks to set
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out rules for the naming of classes and methods within the package. The purpose
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of this, as with all naming standards, is to improve the coherency and
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consistency of the whole API.</p>
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<p>The philosophy of the naming standards is to follow those of
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java.util.Collections.</p>
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<a name="CollectionInterfaces"></a>
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<h3>2. COLLECTION INTERFACES</h3>
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<p>Collection interfaces are new types of collections not included in Java.
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Examples include <code>Bag</code> and <code>SortedBag</code>. These interfaces
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shall:</p>
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<ul>
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<li>be top level interfaces</li>
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<li>have a name that describes their purpose</li>
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</ul>
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<a name="CollectionImplementations"></a>
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<h3>3. COLLECTION IMPLEMENTATIONS</h3>
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<p>Collection implementation are new implementations of collection interfaces.
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Examples include <code>DoubleOrderedMap</code> and <code>DefaultMapBag</code>.
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These interfaces shall:</p>
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<ul>
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<li>be top level classes</li>
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<li>have a name that ends with the collection type being implemented</li>
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<li>have a name that describes their implementation</li>
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<li>contain no public inner classes</li>
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<li>only contain the collection implementation, and any methods specific to
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that implementation</li>
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</ul>
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<a name="UtilityClasses"></a>
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<h3>4. UTILITY CLASSES</h3>
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<p>Utility classes provide additional functionality around an interface and
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its basic implementations. Examples include CollectionUtils and ListUtils.</p>
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<p>Each class shall follow the naming pattern XxxUtils where Xxx relates to the
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object being returned by the class, for example <code>ListUtils</code> and
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<code>BagUtils</code>. Variations on a theme (<code>SortedBag</code> as opposed
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to <code>Bag</code>) will be dealt with in one Utils class. Each Utils class
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shall:</p>
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<ul>
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<li>be a single, static method based, class</li>
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<li>have a name consisting of the interface name plus 'Utils'</li>
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<li>deal with one collection interface and its variations</li>
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<li>provide methods that decorate the interface with additional
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functionality</li>
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<li>provide methods that perform useful utility functions on that
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interface</li>
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</ul>
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2002-07-02 22:34:09 -04:00
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<p>Where the method in a Utils class is a decorator, the name shall consist of
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an adjective followed by the collection type. Typically, such adjective is
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formed by appending an -ed suffix (meaning "having"/"characterized by") to the
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word describing the type of decorator. For example,
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<code>synchronizedMap(Map)</code> or <code>predicatedSet(Set)</code>.
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Occasionally, such construct is awkward and a more suitable adjective can be
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used instead. For example, <code>lazyList</code>,
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<code>unmodifiableList</code>.</p>
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2003-05-10 11:26:44 -04:00
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<p>These decorators should be implemented either as non-public, static,
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inner classes, or as public classes in a subpackage. If a subpackage is used,
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the constructors should be protected and a public static decorate() method
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provided on each class for construction.</p>
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2002-06-28 23:49:01 -04:00
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2004-12-19 16:43:26 -05:00
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<a name="CodingStandards"></a>
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<h3>5. CODING STANDARDS</h3>
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2002-06-28 23:49:01 -04:00
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2004-12-19 16:43:26 -05:00
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<p>Commons Collections follows similar style rules to many other Java open source
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projects, and the Sun conventions. Some specific conventions are:</p>
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2004-12-19 16:43:26 -05:00
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<ul>
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<li>No tabs, 4 space indentations</li>
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<li>Curly brackets open at line end</li>
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<li>Else, catch and finally statements after the closing bracket</li>
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<li>Single space after keyword such as if</li>
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<li>Two spaces between parameter name and description in @param</li>
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2012-06-23 11:49:16 -04:00
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<li>Generally copy the style of the surrounding code</li>
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</ul>
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2012-06-23 11:49:16 -04:00
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<p>And remember, the commons-dev mailing list is there for any discussions
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2004-12-19 16:43:26 -05:00
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or queries about patches or new additions to collections.</p>
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</body>
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</html>
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