Class AvoidStaticImportCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public class AvoidStaticImportCheck
    extends AbstractCheck

    Checks that there are no static import statements.

    Rationale: Importing static members can lead to naming conflicts between class' members. It may lead to poor code readability since it may no longer be clear what class a member resides in (without looking at the import statement).

    If you exclude a starred import on a class this automatically excludes each member individually.

    For example: Excluding java.lang.Math.*. will allow the import of each static member in the Math class individually like java.lang.Math.PI, java.lang.Math.cos, ....

    • Property excludes - Control whether to allow for certain classes via a star notation to be excluded such as java.lang.Math.* or specific static members to be excluded like java.lang.System.out for a variable or java.lang.Math.random for a method. See notes section for details. Type is java.lang.String[]. Default value is "".

    To configure the check:

     <module name="AvoidStaticImport"/>
     

    Example:

     import static java.lang.Math.pow;          // violation
     import static java.lang.System.*;          // violation
     import java.io.File;                       // OK
     import java.util.*;                        // OK
     

    To configure the check so that the java.lang.System.out member and all members from java.lang.Math are allowed:

     <module name="AvoidStaticImport">
       <property name="excludes" value="java.lang.System.out,java.lang.Math.*"/>
     </module>
     

    Example:

     import static java.lang.Math.*;            // OK
     import static java.lang.System.out;        // OK
     import static java.lang.Integer.parseInt;  // violation
     import java.io.*;                          // OK
     import java.util.*;                        // OK
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • import.avoidStatic
    Since:
    5.0
    • Field Detail

      • excludes

        private String[] excludes
        Control whether to allow for certain classes via a star notation to be excluded such as java.lang.Math.* or specific static members to be excluded like java.lang.System.out for a variable or java.lang.Math.random for a method. See notes section for details.
    • Method Detail

      • getAcceptableTokens

        public int[] getAcceptableTokens()
        Description copied from class: AbstractCheck
        The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
        Specified by:
        getAcceptableTokens in class AbstractCheck
        Returns:
        the token set this check is designed for.
        See Also:
        TokenTypes
      • setExcludes

        public void setExcludes​(String... excludes)
        Setter to control whether to allow for certain classes via a star notation to be excluded such as java.lang.Math.* or specific static members to be excluded like java.lang.System.out for a variable or java.lang.Math.random for a method. See notes section for details.
        Parameters:
        excludes - a list of fully-qualified class names/specific static members where static imports are ok
      • isExempt

        private boolean isExempt​(String classOrStaticMember)
        Checks if a class or static member is exempt from known excludes.
        Parameters:
        classOrStaticMember - the class or static member
        Returns:
        true if except false if not
      • isStarImportOfPackage

        private static boolean isStarImportOfPackage​(String classOrStaticMember,
                                                     String exclude)
        Returns true if classOrStaticMember is a starred name of package, not just member name.
        Parameters:
        classOrStaticMember - - full name of member
        exclude - - current exclusion
        Returns:
        true if member in exclusion list