Class PackageDeclarationCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public final class PackageDeclarationCheck
    extends AbstractCheck

    Ensures that a class has a package declaration, and (optionally) whether the package name matches the directory name for the source file.

    Rationale: Classes that live in the null package cannot be imported. Many novice developers are not aware of this.

    Packages provide logical namespace to classes and should be stored in the form of directory levels to provide physical grouping to your classes. These directories are added to the classpath so that your classes are visible to JVM when it runs the code.

    • Property matchDirectoryStructure - Control whether to check for directory and package name match. Type is boolean. Default value is true.

    To configure the check:

     <module name="PackageDeclaration"/>
     

    Let us consider the class AnnotationLocationCheck which is in the directory /com/puppycrawl/tools/checkstyle/checks/annotations/

     package com.puppycrawl.tools.checkstyle.checks; //Violation
     public class AnnotationLocationCheck extends AbstractCheck {
       //...
     }
     

    Example of how the check works when matchDirectoryStructure option is set to false. Let us again consider the AnnotationLocationCheck class located at directory /com/puppycrawl/tools/checkstyle/checks/annotations/ along with the following setup,

     <module name="PackageDeclaration">
     <property name="matchDirectoryStructure" value="false"/>
     </module>
     
     package com.puppycrawl.tools.checkstyle.checks;  //No Violation
    
     public class AnnotationLocationCheck extends AbstractCheck {
       //...
     }
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • mismatch.package.directory
    • missing.package.declaration
    Since:
    3.2