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version 3.0 documentation

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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Miscellaneous Checks</title>
<link rel="stylesheet" type="text/css" href="mystyle.css">
<link rel="stylesheet" type="text/css" href="mystyle.css"/>
</head>
<body>
<h1>Miscellaneous Checks</h1>
<!-- The header -->
<table border="0" width="100%" summary="header layout">
<tr>
<td><h1>Miscellaneous Checks</h1></td>
<td align="right"><img src="logo.png" alt="Checkstyle Logo"/></td>
</tr>
</table>
<!-- content -->
<table border="0" width="100%" cellpadding="5" summary="body layout">
<tr>
<!--Left menu-->
<td class="menu" valign="top">
<ul>
<li>
<a href="#EqualsHashCode">EqualsHashCode</a>
</li>
<li>
<a href="#GenericIllegalRegexp">GenericIllegalRegexp</a>
</li>
<li>
<a href="#HiddenField">HiddenField</a>
</li>
<li>
<a href="#IllegalInstantiation">IllegalInstantiation</a>
</li>
<li>
<a href="#InnerAssignment">InnerAssignment</a>
</li>
<li>
<a href="#SimplifyBooleanExpression">SimplifyBooleanExpression</a>
</li>
<li>
<a href="#SimplifyBooleanReturn">SimplifyBooleanReturn</a>
</li>
<li>
<a href="#TodoComment">TodoComment</a>
</li>
<li>
<a href="#Translation">Translation</a>
</li>
<li>
<a href="#UpperEll">UpperEll</a>
</li>
</ul>
</td>
<!--Content-->
<td class="content" valign="top" align="left"><a name="EqualsHashCode"></a> <h2>EqualsHashCode</h2>
<h4>Description</h4>
<p class="body">
Checks that classes that override <span class="code">equals()</span> also
override <span class="code">hashCode()</span>.
</p>
<p class="body">
Rationale: The contract of <span class="code">equals()</span> and <span class="code">
hashCode()</span> requires that equal objects have the same hashCode. Hence,
whenever you override <span class="code">equals()</span> you must override <span class="code">
hashCode()</span> to ensure that your class can be used in collections that are
hash based.
</p>
<h2>To-do comments</h2>
<h4>Example</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;EqualsHashCode&quot;/&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
TreeWalker
</p>
<!-- --> <a name="GenericIllegalRegexp"></a> <h2>GenericIllegalRegexp</h2> <h4>Description</h4>
<p class="body">
A generic check for code problems - the user can search for any pattern. This is
similar to a recursive grep, only that it's integrated in checkstyle.
</p>
<p class="body">
Rationale: This check can be used to prototype checks and to find common bad
practice such as calling <span class="code">ex.printStacktrace()</span>, <span class="code">
System.out.println()</span>, <span class="code">System.exit()</span>, etc.
</p>
<h4>Properties</h4>
<table width="100%" border="1" cellpadding="5" class="body">
<tr class="header">
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>format</td>
<td>illegal pattern</td>
<td><a href="property_types.html#regexp">regular expression</a></td>
<td><span class="default">^$</span> (empty)</td>
</tr>
</table>
<h4>Example</h4>
<p class="body">
To configure the check for calls to <span class="code">System.out.println</span>:
</p>
<pre class="body">
&lt;module name=&quot;GenericIllegalRegexp&quot;&gt;
&lt;property name=&quot;format&quot; value=&quot;System\.out\.println&quot;/&gt;
&lt;/module&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
TreeWalker
</p>
<!-- --> <a name="HiddenField"></a> <h2>HiddenField</h2> <h4>Description</h4>
<p class="body">
Checks that a local variable or a parameter does not shadow a field that is
defined in the same class.
</p>
<h4>Properties</h4>
<table width="100%" border="1" cellpadding="5" class="body">
<tr class="header">
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>tokens</td>
<td>tokens to check</td>
<td>subset of tokens PARAMETER_DEF, VARIABLE_DEF</td>
<td>PARAMETER_DEF, VARIABLE_DEF</td>
</tr>
</table>
<h4>Examples</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;HiddenField&quot;/&gt;
</pre>
<p class="body">
To configure the check so that it checks local variables but not parameters:
</p>
<pre class="body">
&lt;module name=&quot;HiddenField&quot;&gt;
&lt;property name=&quot;tokens&quot; value=&quot;VARIABLE_DEF&quot;/&gt;
&lt;/module&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
TreeWalker
</p>
<!-- --> <a name="IllegalInstantiation"></a> <h2>IllegalInstantiation</h2> <h4>Description</h4>
<p class="body">
Checks for illegal instantiations where a factory method is preferred.
</p>
<p class="body">
Rationale: Depending on the project, for some classes it might be preferable to
create instances through factory methods rather than calling the constructor.
</p>
<p class="body">
A simple example is the <span class="code">java.lang.Boolean</span> class. In
order to save memory and CPU cycles, it is preferable to use the predefined
constants <span class="code">
TRUE</span> and <span class="code">FALSE</span>. Constructor invocations should
be replaced by calls to <span class="code">Boolean.valueOf()</span>.
</p>
<p class="body">
Some extremely performance sensitive projects may require the use of factory
methods for other classes as well, to enforce the usage of number caches or
object pools.
</p>
<h4>Notes</h4>
<p class="body">
There is a limitation that it is currently not possible to specify array classes.
</p>
<h4>Example</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;IllegalInstantiation&quot;/&gt;
</pre>
<p>The property <span class="code">checkstyle.pattern.todo</span> specifies
the pattern to match for to-do comments. The property type is
<a href="property_types.html#regexp">regular expression</a> and defaults to
<span class="default">TODO:</span>.</p>
<div class="tip">
<h4 class="tip">Tip</h4>
<p>Using to-do comments is a great way to keep track of tasks that need to be
done. By having them reported by Checkstyle makes it very hard to forget about
them.</p>
</div>
<h2>Integer Literals</h2>
<p>The property <span class="code">checkstyle.ignore.longell</span> specifies
whether to not require that long integer literals use an uppercase
<span class="code">L</span>. For example <span class="code">40L</span> instead
of <span class="code">40l</span>. This is in accordance to the Java Language
Specification,
<a href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html#48282">Section 3.10.1</a>.
The property type is <a href="property_types.html#boolean">boolean</a> and
defaults to <span class="default">false</span>.</p>
<h2>illegal Instantiations</h2>
<p>The property <span class="code">checkstyle.illegal.instantiations</span>
contains the set of classes that should not be instantiated directly. The
property type is <a href="property_types.html#stringSet">string set</a> and
defaults to an empty set.</p>
<div class="tip">
<h4 class="tip">Tip</h4>
<p>A common mistake is to create new instances of <span
class="code">java.lang.Boolean</span> instead of using the constants <span
class="code">TRUE</span> and <span class="code">FALSE</span> or the <span
class="code">Boolean.valueOf()</span> factory methods. This increases the
program's memory requirements and wastes CPU cycles during memory allocation
and garbage collection.</p> <p>To find this error automatically, include <span
class="code">java.lang.Boolean</span> in the list of illegal
instantiations.</p>
</div>
<hr>
<p align="center">Copyright &copy; 2002 Oliver Burn. All rights Reserved.</p>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
TreeWalker
</p>
<!-- --> <a name="InnerAssignment"></a> <h2>InnerAssignment</h2> <h4>Description</h4>
<p class="body">
Checks for assignments in subexpressions, such as in <span class="code">String s
= Integer.toString(i = 2);</span>.
</p>
<p class="body">
Rationale: With the exception of <span class="code">for</span> iterators, all
assignments should occur in their own toplevel statement to increase readability.
With inner assignments like the above it is difficult to see all places where a
variable is set.
</p>
<h4>Properties</h4>
<table width="100%" border="1" cellpadding="5" class="body">
<tr class="header">
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>tokens</td>
<td>assignments to check</td>
<td>subset of tokens ASSIGN, BAND_ASSIGN, BOR_ASSIGN, BSR_ASSIGN, BXOR_ASSIGN,
DIV_ASSIGN, MINUS_ASSIGN, MOD_ASSIGN, PLUS_ASSIGN, SL_ASSIGN, SR_ASSIGN,
STAR_ASSIGN</td>
<td>all tokens</td>
</tr>
</table>
<h4>Examples</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;InnerAssignment&quot;/&gt;
</pre>
<p class="body">
To configure the check for only <span class="code">=</span>, <span class="code">
+=</span>, and <span class="code">-=</span> operators:
</p>
<pre class="body">
&lt;module name=&quot;InnerAssignment&quot;&gt;
&lt;property name=&quot;tokens&quot; value=&quot;ASSIGN,PLUS_ASSIGN,MINUS_ASSIGN&quot;/&gt;
&lt;/module&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
TreeWalker
</p>
<!-- --> <a name="SimplifyBooleanExpression"></a> <h2>SimplifyBooleanExpression</h2>
<h4>Description</h4>
<p class="body">
Checks for overly complicated boolean expressions. Currently finds code like <span class="code">
if (b == true)</span>, <span class="code">b || true</span>, <span class="code">!false</span>, etc.
</p>
<p class="body">
Rationale: Complex boolean logic makes code hard to understand and maintain.
</p>
<h4>Example</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;SimplifyBooleanExpression&quot;/&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
TreeWalker
</p>
<!-- --> <a name="SimplifyBooleanReturn"></a> <h2>SimplifyBooleanReturn</h2> <h4>Description</h4>
<p class="body">
Checks for overly complicated boolean return statements. Idea shamelessly stolen
from the equivalent <a href="http://pmd.sourceforge.net">PMD rule</a>.
</p>
<h4>Example</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;SimplifyBooleanReturn&quot;/&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
TreeWalker
</p>
<!-- --> <a name="TodoComment"></a> <h2>TodoComment</h2> <h4>Description</h4>
<p class="body">
A check for <span class="code">TODO:</span> comments. Actually it is a generic <a href="http://jakarta.apache.org/regexp/apidocs/org/apache/regexp/RE.html">regular
expression</a> matcher on Java comments. To check for other patterns in Java
comments, set property format.
</p>
<h4>Properties</h4>
<table width="100%" border="1" cellpadding="5" class="body">
<tr class="header">
<th>name</th>
<th>description</th>
<th>type</th>
<th>default value</th>
</tr>
<tr>
<td>format</td>
<td>pattern to check</td>
<td><a href="property_types.html#regexp">regular expression</a></td>
<td><span class="default">TODO:</span></td>
</tr>
</table>
<h4>Notes</h4>
<p class="body">
Using <span class="code">TODO:</span> comments is a great way to keep track of
tasks that need to be done. Having them reported by Checkstyle makes it very
hard to forget about them.
</p>
<h4>Examples</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;TodoComment&quot;/&gt;
</pre>
<p class="body">
To configure the check for comments that contain <span class="code">WARNING</span>:
</p>
<pre class="body">
&lt;module name=&quot;TodoComment&quot;&gt;
&lt;property name=&quot;format&quot; value=&quot;WARNING&quot;/&gt;
&lt;/module&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
TreeWalker
</p>
<!-- --> <a name="Translation"></a> <h2>Translation</h2> <h4>Description</h4>
<p class="body">
A <a href="config.html#overview">FileSetCheck</a> that ensure the correct
translation of code by checking property files for consistency regarding their
keys. Two property files describing one and the same context are consistent if
they contain the same keys.
</p>
<h4>Example</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;Translation&quot;/&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
Checker
</p>
<!-- --> <a name="UpperEll"></a> <h2>UpperEll</h2> <h4>Description</h4>
<p class="body">
Checks that long constants are defined with an upper ell. That is <span class="code">'
L'</span> and
not <span class="code">'l'</span>. This is in accordance to the Java Language
Specification, <a href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html#48282">
Section
3.10.1</a>.
</p>
<p class="body"> Rationale: The letter <span class="code">l</span> looks a lot
like <span class="code">1</span>.
</p>
<h4>Examples</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;UpperEll&quot;/&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
TreeWalker
</p>
</td>
</tr>
</table>
<hr />
<p>
Copyright &copy; 2002 Oliver Burn. All rights Reserved.
</p>
</body>
</html>