# Naming Conventions

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## Overview

Each of these naming modules validates identifiers for particular code elements. Valid identifiers for a naming module are specified by its format property. The value of format is a regular expression for valid identifiers. This is an example of a configuration of the MemberName module to ensure that member identifiers begin with 'm', followed by an upper case letter, and then letters and digits:

    <module name="MemberName">
      <property name="format" value="^m[A-Z][a-zA-Z0-9]*$"/>
    </module>

All naming modules belong to package com.puppycrawl.tools.checkstyle.checks.naming and are submodules of TreeWalker.

## Modules

module | validates identifiers for | default value of format
--- | --- | ---
AbstractClassName | abstract classes | ^Abstract.*$|^.*Factory$
ConstantName | constants (static, final fields) | ^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$
LocalFinalVariableName | local, final variables, including catch parameters | ^[a-z][a-zA-Z0-9]*$
LocalVariableName | local, non-final variables, including catch parameters | ^[a-z][a-zA-Z0-9]*$
MemberName | non-static fields | ^[a-z][a-zA-Z0-9]*$
MethodName | methods | ^[a-z][a-zA-Z0-9]*$
PackageName | packages | ^[a-z]+(\.[a-zA-Z_][a-zA-Z0-9_]*)*$
ParameterName | parameters | ^[a-z][a-zA-Z0-9]*$
StaticVariableName | static, non-final fields | ^[a-z][a-zA-Z0-9]*$
TypeName | classes and interfaces | ^[A-Z][a-zA-Z0-9]*$

## Notes

The default value of format for module PackageName has been chosen to match the requirements in the Java Language specification and the Sun coding conventions. However both underscores and uppercase letters are rather uncommon, so most configurations should probably assign value ^[a-z]+(\.[a-z][a-z0-9]*)*$ to format for module PackageName, as in

    <module name="PackageName">
        <property name="format"
                  value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
    </module>

Module LocalVariableName also has property tokens which can be used to control whether the check applies to variable declarations or catch clause parameters through tokens VARIABLE_DEF and PARAMETER_DEF. For example, the following configuration element ensures that catch clause parameters begin with "e", followed by letters and digits:

    <module name="LocalVariableName">
        <property name="format" value="^e[a-zA-Z0-9]*$"/>
        <property name="tokens" value="PARAMETER_DEF"/>
    </module>

Module TypeName also has property tokens which can be used to control whether the check applies to classes or interfaces through tokens CLASS_DEF and INTERFACE_DEF. For example, the following configuration element ensures that interface names begin with "I_", followed by letters and digits:

    <module name="TypeName">
        <property name="format"
                  value="^I_[a-zA-Z0-9]*$"/>
        <property name="tokens"
                  value="INTERFACE_DEF"/>
    </module>

Module MemberName also has the following properties:

name | description | type | default value
--- | --- | --- | ---
applyToPublic | Controls whether to apply the check to public member. | Boolean | true
applyToProtected | Controls whether to apply the check to protected member. | Boolean | true
applyToPackage | Controls whether to apply the check to package-private member. | Boolean | true
applyToPrivate | Controls whether to apply the check to pribvate member. | Boolean | true

Copyright © 2001-2007, Oliver Burn