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]*$"/>
</module>
All naming modules belong to package com.puppycrawl.tools.checkstyle.checks.naming and are submodules of TreeWalker.
| module | validates identifiers for | default value of format |
|---|---|---|
| AbstractClassName | abstract classes | ^Abstract.+$|^.*Factory$ |
| ClassTypeParameterName | class type parameters | ^[A-Z]$ |
| 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]*$ |
| MethodTypeParameterName | method type parameters | ^[A-Z]$ |
| InterfaceTypeParameterName | interface type parameters | ^[A-Z]$ |
| 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, interfaces, enums, and annotations | ^[A-Z][a-zA-Z0-9]*$ |
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]*$"/>
<property name="tokens" value="PARAMETER_DEF"/>
</module>
The check provides the following properties:
| name | description | type | default value |
|---|---|---|---|
| allowOneCharVarInForLoop |
Allow one character variable name in initialization expressions in FOR loop. For example:
for (int i = 1; i < 10; i++) {}
|
Boolean | false |
An example of how to configure the check to allow one character variable name in initialization expressions in FOR loop:
<module name="LocalVariableName">
<property name="allowOneCharVarInForLoop" value="true"/>
</module>
Module TypeName also has property
tokens, which can be used to control the kind of type
that the check applies to. The value of the tokens
property is a comma-separated list of one or more of the following
tokens: CLASS_DEF, INTERFACE_DEF,
ENUM_DEF, ANNOTATION_DEF.
For example, the following configuration element ensures that
interface names begin with "I_", followed by
letters and digits:
<module name="TypeName">
<property name="format"
value="^I_[a-zA-Z0-9]*$"/>
<property name="tokens"
value="INTERFACE_DEF"/>
</module>
Module MethodName also has the following properties:
| name | description | type | default value |
|---|---|---|---|
| allowClassName |
Controls whether to allow a method name to have the same
name as the residing class name. This is not to be confused
with a constructor. An easy mistake is to place a return
type on a constructor declaration which turns it into a
method. For example:
class MyClass {
public void MyClass() {} //this is a method
public MyClass() {} //this is a constructor
}
|
Boolean | false |
Module AbstractClassName also has the following properties:
| name | description | type | default value |
|---|---|---|---|
| ignoreModifier | Controls whether to ignore checking for the abstract modifier on classes that match the name. | Boolean | false |
| ignoreName | Controls whether to ignore checking the name. Realistically only useful if using the check to identify that match name and do not have the abstract modifier. name. | Boolean | false |
The following example shows how to configure the AbstractClassName to checks names, but ignore missing abstract modifiers:
<module name="AbstractClassName">
<property name="ignoreModifier" value="true"/>
</module>
The modules ConstantName, MemberName, StaticVariableName and TypeName also have 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 private member. | Boolean | true |
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>
The Check validate abbreviations(consecutive capital letters) length in identifier name, it also allows to enforce camel case naming. Please read more at Google Style Guide to get to know how to avoid long abbreviations in names.
| name | description | type | default value |
|---|---|---|---|
| allowedAbbreviationLength | indicates on the allowed amount of capital letters in targeted identifiers (abbreviations in the classes, interfaces, variables and methods names, ... ). | 3 | true |
| allowedAbbreviations | list of abbreviations that must be skipped for checking. Abbreviations should be separated by comma, no spaces are allowed. | stringSet | null |
| ignoreFinal | allow to skip variables with final modifier. | Boolean | true |
| ignoreStatic | allow to skip variables with static modifier. | Boolean | true |
| ignoreOverriddenMethod | Allows to ignore methods tagged with @Override annotation (that usually mean inherited name). | Boolean | true |
Default configuration
<module name="AbbreviationAsWordInName"/>
To configure to check variables and classes identifiers, do not ignore variables with static modifier and allow no abbreviations (enforce camel case phrase) and allow no abbreviations to use (camel case phrase) and allow XML and URL abbreviations.
<module name="AbbreviationAsWordInName">
<property name="tokens" value="VARIABLE_DEF,CLASS_DEF"/>
<property name="ignoreStatic" value="false"/>
<property name="allowedAbbreviationLength" value="1"/>
<property name="allowedAbbreviation" value="XML,URL"/>
</module>