Package com.puppycrawl.tools.checkstyle.checks.modifier

Class InterfaceMemberImpliedModifierCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable
    public class InterfaceMemberImpliedModifierCheck
extends AbstractCheck

    Checks for implicit modifiers on interface members and nested types.

    This check is effectively the opposite of RedundantModifier. It checks the modifiers on interface members, ensuring that certain modifiers are explicitly specified even though they are actually redundant.

    Methods in interfaces are public by default, however from Java 9 they can also be private. This check provides the ability to enforce that public is explicitly coded and not implicitly added by the compiler.

    From Java 8, there are three types of methods in interfaces - static methods marked with static, default methods marked with default and abstract methods which do not have to be marked with anything. From Java 9, there are also private methods marked with private. This check provides the ability to enforce that abstract is explicitly coded and not implicitly added by the compiler.

    Fields in interfaces are always public static final and as such the compiler does not require these modifiers. This check provides the ability to enforce that these modifiers are explicitly coded and not implicitly added by the compiler.

    Nested types within an interface are always public static and as such the compiler does not require the public static modifiers. This check provides the ability to enforce that the public and static modifiers are explicitly coded and not implicitly added by the compiler. 

     public interface AddressFactory {
   // check enforces code contains "public static final"
   public static final String UNKNOWN = "Unknown";

   String OTHER = "Other";  // violation

   // check enforces code contains "public" or "private"
   public static AddressFactory instance();

   // check enforces code contains "public abstract"
   public abstract Address createAddress(String addressLine, String city);

   List<Address> findAddresses(String city);  // violation

   // check enforces default methods are explicitly declared "public"
   public default Address createAddress(String city) {
     return createAddress(UNKNOWN, city);
   }

   default Address createOtherAddress() {  // violation
     return createAddress(OTHER, OTHER);
   }
 }

    Rationale for this check: Methods, fields and nested types are treated differently depending on whether they are part of an interface or part of a class. For example, by default methods are package-scoped on classes, but public in interfaces. However, from Java 8 onwards, interfaces have changed to be much more like abstract classes. Interfaces now have static and instance methods with code. Developers should not have to remember which modifiers are required and which are implied. This check allows the simpler alternative approach to be adopted where the implied modifiers must always be coded explicitly.

    • Property violateImpliedPublicField - Control whether to enforce that public is explicitly coded on interface fields. Type is boolean. Default value is true.
    • Property violateImpliedStaticField - Control whether to enforce that static is explicitly coded on interface fields. Type is boolean. Default value is true.
    • Property violateImpliedFinalField - Control whether to enforce that final is explicitly coded on interface fields. Type is boolean. Default value is true.
    • Property violateImpliedPublicMethod - Control whether to enforce that public is explicitly coded on interface methods. Type is boolean. Default value is true.
    • Property violateImpliedAbstractMethod - Control whether to enforce that abstract is explicitly coded on interface methods. Type is boolean. Default value is true.
    • Property violateImpliedPublicNested - Control whether to enforce that public is explicitly coded on interface nested types. Type is boolean. Default value is true.
    • Property violateImpliedStaticNested - Control whether to enforce that static is explicitly coded on interface nested types. Type is boolean. Default value is true.

    To configure the check so that it checks that all implicit modifiers on methods, fields and nested types are explicitly specified in interfaces.

    Configuration: 

     <module name="InterfaceMemberImpliedModifier"/>

    Code: 

     public interface AddressFactory {

   public static final String UNKNOWN = "Unknown";  // valid

   String OTHER = "Other";  // violation

   public static AddressFactory instance();  // valid

   public abstract Address createAddress(String addressLine, String city);  // valid

   List<Address> findAddresses(String city);  // violation

   interface Address {  // violation

     String getCity();  // violation
   }
 }

    This example checks that all implicit modifiers on methods and fields are explicitly specified, but nested types do not need to be.

    Configuration: 

     <module name="InterfaceMemberImpliedModifier">
   <property name="violateImpliedPublicNested" value="false"/>
   <property name="violateImpliedStaticNested" value="false"/>
 </module>

    Code: 

     public interface RoadFeature {

   String STOP = "Stop";  // violation

   enum Lights {  // valid because of configured properties

     RED, YELLOW, GREEN;
   }
 }

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • interface.implied.modifier
    Since:
    8.12

    • Field Detail

      • MSG_KEY

        public static final java.lang.String MSG_KEY
        A key is pointing to the warning message text in "messages.properties" file.
        See Also:
        Constant Field Values

    • Constructor Detail

      • InterfaceMemberImpliedModifierCheck

        public InterfaceMemberImpliedModifierCheck()

    • Method Detail

      • setViolateImpliedPublicField

        public void setViolateImpliedPublicField​(boolean violateImpliedPublicField)
        Setter to control whether to enforce that public is explicitly coded on interface fields.
        Parameters:
        violateImpliedPublicField - True to perform the check, false to turn the check off.

      • setViolateImpliedStaticField

        public void setViolateImpliedStaticField​(boolean violateImpliedStaticField)
        Setter to control whether to enforce that static is explicitly coded on interface fields.
        Parameters:
        violateImpliedStaticField - True to perform the check, false to turn the check off.

      • setViolateImpliedFinalField

        public void setViolateImpliedFinalField​(boolean violateImpliedFinalField)
        Setter to control whether to enforce that final is explicitly coded on interface fields.
        Parameters:
        violateImpliedFinalField - True to perform the check, false to turn the check off.

      • setViolateImpliedPublicMethod

        public void setViolateImpliedPublicMethod​(boolean violateImpliedPublicMethod)
        Setter to control whether to enforce that public is explicitly coded on interface methods.
        Parameters:
        violateImpliedPublicMethod - True to perform the check, false to turn the check off.

      • setViolateImpliedAbstractMethod

        public void setViolateImpliedAbstractMethod​(boolean violateImpliedAbstractMethod)
        Setter to control whether to enforce that abstract is explicitly coded on interface methods.
        Parameters:
        violateImpliedAbstractMethod - True to perform the check, false to turn the check off.

      • setViolateImpliedPublicNested

        public void setViolateImpliedPublicNested​(boolean violateImpliedPublicNested)
        Setter to control whether to enforce that public is explicitly coded on interface nested types.
        Parameters:
        violateImpliedPublicNested - True to perform the check, false to turn the check off.

      • setViolateImpliedStaticNested

        public void setViolateImpliedStaticNested​(boolean violateImpliedStaticNested)
        Setter to control whether to enforce that static is explicitly coded on interface nested types.
        Parameters:
        violateImpliedStaticNested - True to perform the check, false to turn the check off.

      • getDefaultTokens

        public int[] getDefaultTokens()
        Description copied from class: AbstractCheck
        Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.
        Specified by:
        getDefaultTokens in class AbstractCheck
        Returns:
        the default tokens
        See Also:
        TokenTypes

      • getRequiredTokens

        public int[] getRequiredTokens()
        Description copied from class: AbstractCheck
        The tokens that this check must be registered for.
        Specified by:
        getRequiredTokens in class AbstractCheck
        Returns:
        the token set this must be registered for.
        See Also:
        TokenTypes

      • 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