PackageName

Since Checkstyle 3.0

Description

Checks that package names conform to a specified pattern.

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.

Properties

name description type default value since
format Control the pattern to match valid identifiers. Pattern "^[a-z]+(\.[a-zA-Z_]\w*)*$" 3.0

Examples

To configure the check: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="PackageName"/>
  </module>
</module>

Code Example:

package com; // OK
package COM; // violation, name 'COM' must match pattern '^[a-z]+(\.[a-zA-Z_]\w*)*$'
package com.checkstyle.checks; // OK
package com.A.checkstyle.checks; // OK
package com.checkstyle1.checks; // OK
package com.checkSTYLE.checks; // OK
package com._checkstyle.checks_; // OK

An example of how to configure the check to ensure with packages start with a lowercase letter and only contains lowercase letters or numbers is: 

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

Code Example:

package com; // OK
package COM; // violation, name 'COM' must match pattern '^[a-z]+(\.[a-z][a-z0-9]*)*$'
package com.checkstyle.checks; // OK
package com.A.checkstyle.checks; // violation, name 'com.A.checkstyle' must match
                                 // pattern '^[a-z]+(\.[a-z][a-z0-9]*)*$'
package com.checkstyle1.checks; // OK
package com.checkSTYLE.checks; // violation, name 'com.checkSTYLE.checks' must
                               // match pattern '^[a-z]+(\.[a-z][a-z0-9]*)*$'
package com._checkstyle.checks_; // violation, name 'com._checkstyle.checks_' must match
                                 // pattern '^[a-z]+(\.[a-z][a-z0-9]*)*$'

Example of Usage

Violation Messages

All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.

Package

com.puppycrawl.tools.checkstyle.checks.naming

Parent Module

TreeWalker