205 lines
6.3 KiB
HTML
205 lines
6.3 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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"DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
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<head>
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<title>Checks for imports</title>
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<link rel="stylesheet" type="text/css" href="mystyle.css"/>
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</head>
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<body>
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<!-- The header -->
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<table border="0" width="100%" summary="header layout">
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<tr>
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<td><h1>Checks for imports</h1></td>
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<td align="right"><img src="logo.png" alt="Checkstyle Logo"/></td>
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</tr>
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</table>
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<!-- content -->
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<table border="0" width="100%" cellpadding="5" summary="body layout">
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<tr>
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<!--Left menu-->
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<td class="menu" valign="top">
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<ul>
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<li>
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<a href="#AvoidStarImport">AvoidStarImport</a>
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</li>
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<li>
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<a href="#IllegalImport">IllegalImport</a>
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</li>
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<li>
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<a href="#RedundantImport">RedundantImport</a>
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</li>
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<li>
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<a href="#UnusedImports">UnusedImports</a>
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</li>
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</ul>
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</td>
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<!--Content-->
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<td class="content" valign="top" align="left">
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<a name="AvoidStarImport"></a> <h2>AvoidStarImport</h2>
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<h4>Description</h4>
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<p class="body">
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Checks that there are no import statements that use the * notation.
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</p>
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<p class="body">
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Rationale: Importing all classes from a package leads to tight coupling
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between packages and might lead to problems when a new version of a library
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introduces name clashes.
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</p>
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<h4>Example</h4>
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<p class="body">
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To configure the check:
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</p>
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<pre class="body">
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<module name="AvoidStarImport"/>
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</pre>
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<h4>Package</h4>
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<p class="body">
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com.puppycrawl.tools.checkstyle.checks
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</p>
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<h4>Parent Module</h4>
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<p class="body">
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<a href="config.html#treewalker">TreeWalker</a>
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</p>
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<a name="IllegalImport"></a> <h2>IllegalImport</h2>
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<h4>Description</h4>
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<p class="body">
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Checks for imports from a set of illegal packages. By default, the check rejects
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all <span class="code">sun.*</span> packages since programs that contain direct
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calls to the <span class="code">sun.*</span> packages are <a href="http://java.sun.com/products/jdk/faq/faq-sun-packages.html">not
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100% Pure Java</a>. To reject other packages, set property <span class="code">
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illegalPkgs</span> to a list of the illegal packages.
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</p>
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<h4>Properties</h4>
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<table width="100%" border="1" cellpadding="5" class="body">
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<tr class="header">
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<th>name</th>
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<th>description</th>
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<th>type</th>
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<th>default value</th>
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</tr>
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<tr>
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<td>illegalPkgs</td>
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<td>packages to reject</td>
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<td><a href="property_types.html#stringSet">list of strings</a></td>
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<td><span class="default">sun</span></td>
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</tr>
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</table>
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<h4>Examples</h4>
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<p class="body">
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To configure the check:
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</p>
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<pre class="body">
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<module name="IllegalImport"/>
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</pre>
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<p class="body">
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To configure the check so that it rejects packages <span class="code">java.io.*</span>
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and <span class="code">java.sql.*</span>:
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</p>
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<pre class="body">
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<module name="IllegalImport">
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<property name="illegalPkgs" value="java.io, java.sql"/>
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</module>
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</pre>
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<h4>Package</h4>
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<p class="body">
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com.puppycrawl.tools.checkstyle.checks
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</p>
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<h4>Parent Module</h4>
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<p class="body">
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<a href="config.html#treewalker">TreeWalker</a>
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</p>
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<a name="RedundantImport"></a> <h2>RedundantImport</h2> <h4>Description</h4>
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<p class="body">
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Checks for redundant import statements. An import statement is considered
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redundant if:
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</p>
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<ul class="body">
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<li>
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It is a duplicate of another import. This is, when a class is imported more than
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once.
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</li>
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<li>
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The class imported is from the <span class="code">java.lang</span> package, e.g.
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importing <span class="code">java.lang.String</span>.
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</li>
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<li>
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The class imported is from the same package.
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</li>
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</ul>
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<h4>Example</h4>
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<p class="body">
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To configure the check:
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</p>
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<pre class="body">
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<module name="RedundantImport"/>
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</pre>
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<h4>Package</h4>
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<p class="body">
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com.puppycrawl.tools.checkstyle.checks
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</p>
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<h4>Parent Module</h4>
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<p class="body">
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<a href="config.html#treewalker">TreeWalker</a>
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</p>
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<a name="UnusedImports"></a> <h2>UnusedImports</h2> <h4>Description</h4>
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<p class="body">
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Checks for unused import statements. Checkstyle uses a simple but very reliable
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algorithm to report on unused import statements. An import statement is
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considered unused if:
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</p>
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<ul class="body">
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<li>
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It is not referenced in the file. The algorithm does not support wild-card
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imports like <span class="code">import java.io.*;</span>. Most IDE's provide
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very sophisticated checks for imports that handle wild-card imports.
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</li>
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<li>
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It is a duplicate of another import. This is when a class is imported more than
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once.
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</li>
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<li>
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The class imported is from the <span class="code">java.lang</span> package. For
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example importing <span class="code">java.lang.String</span>.
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</li>
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<li>
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The class imported is from the same package.
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</li>
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</ul>
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<h4>Example</h4>
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<p class="body">
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To configure the check:
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</p>
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<pre class="body">
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<module name="UnusedImports"/>
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</pre>
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<h4>Package</h4>
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<p class="body">
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com.puppycrawl.tools.checkstyle.checks
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</p>
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<h4>Parent Module</h4>
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<p class="body">
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<a href="config.html#treewalker">TreeWalker</a>
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</p>
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</td>
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</tr>
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</table>
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<hr />
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<div><a href="index.html">Back to the Checkstyle Home Page</a></div>
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<p class="copyright">
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Copyright © 2002-2003 Oliver Burn. All rights Reserved.
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</p>
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</body>
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</html>
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