code: ///////////////////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
  // Copyright (C) 2001-2023 the original author or authors.
  //
  // This library is free software; you can redistribute it and/or
  // modify it under the terms of the GNU Lesser General Public
  // License as published by the Free Software Foundation; either
  // version 2.1 of the License, or (at your option) any later version.
  //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.checks.modifier;
  
  import com.puppycrawl.tools.checkstyle.StatelessCheck;
  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
  
  /**
   * <p>
   * Checks for implicit modifiers on interface members and nested types.
   * </p>
   * <p>
   * This check is effectively the opposite of
   * <a href="https://checkstyle.org/checks/modifier/redundantmodifier.html#RedundantModifier">
   * RedundantModifier</a>.
   * It checks the modifiers on interface members, ensuring that certain modifiers are explicitly
   * specified even though they are actually redundant.
   * </p>
   * <p>
   * Methods in interfaces are {@code public} by default, however from Java 9 they can also be
   * {@code private}. This check provides the ability to enforce that {@code public} is explicitly
   * coded and not implicitly added by the compiler.
   * </p>
   * <p>
   * From Java 8, there are three types of methods in interfaces - static methods marked with
   * {@code static}, default methods marked with {@code default} and abstract methods which do not
   * have to be marked with anything. From Java 9, there are also private methods marked with
   * {@code private}. This check provides the ability to enforce that {@code abstract} is
   * explicitly coded and not implicitly added by the compiler.
   * </p>
   * <p>
   * Fields in interfaces are always {@code 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.
   * </p>
   * <p>
   * Nested types within an interface are always {@code public static} and as such the compiler
   * does not require the {@code public static} modifiers. This check provides the ability to
   * enforce that the {@code public} and {@code static} modifiers are explicitly coded and not
   * implicitly added by the compiler.
   * </p>
   * <pre>
   * 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&lt;Address&gt; 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);
   *   }
   * }
   * </pre>
   * <p>
   * 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.
   * </p>
   * <ul>
   * <li>
   * Property {@code violateImpliedPublicField} - Control whether to enforce that {@code public}
   * is explicitly coded on interface fields.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * <li>
   * Property {@code violateImpliedStaticField} - Control whether to enforce that {@code static}
   * is explicitly coded on interface fields.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * <li>
   * Property {@code violateImpliedFinalField} - Control whether to enforce that {@code final}
   * is explicitly coded on interface fields.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * <li>
   * Property {@code violateImpliedPublicMethod} - Control whether to enforce that {@code public}
   * is explicitly coded on interface methods.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * <li>
   * Property {@code violateImpliedAbstractMethod} - Control whether to enforce that {@code abstract}
   * is explicitly coded on interface methods.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * <li>
   * Property {@code violateImpliedPublicNested} - Control whether to enforce that {@code public}
   * is explicitly coded on interface nested types.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * <li>
   * Property {@code violateImpliedStaticNested} - Control whether to enforce that {@code static}
   * is explicitly coded on interface nested types.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * </ul>
   * <p>
   * To configure the check so that it checks that all implicit modifiers on methods, fields
   * and nested types are explicitly specified in interfaces.
   * </p>
   * <p>
   * Configuration:
   * </p>
   * <pre>
   * &lt;module name=&quot;InterfaceMemberImpliedModifier&quot;/&gt;
   * </pre>
   * <p>
   * Code:
   * </p>
   * <pre>
   * 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&lt;Address&gt; findAddresses(String city);  // violation
   *
   *   interface Address {  // violation
   *
   *     String getCity();  // violation
   *   }
   * }
   * </pre>
   * <p>
   * This example checks that all implicit modifiers on methods and fields are
   * explicitly specified, but nested types do not need to be.
   * </p>
   * <p>
   * Configuration:
   * </p>
   * <pre>
   * &lt;module name=&quot;InterfaceMemberImpliedModifier&quot;&gt;
   *   &lt;property name=&quot;violateImpliedPublicNested&quot; value=&quot;false&quot;/&gt;
   *   &lt;property name=&quot;violateImpliedStaticNested&quot; value=&quot;false&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Code:
   * </p>
   * <pre>
   * public interface RoadFeature {
   *
   *   String STOP = "Stop";  // violation
   *
   *   enum Lights {  // valid because of configured properties
   *
   *     RED, YELLOW, GREEN;
   *   }
   * }
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code interface.implied.modifier}
   * </li>
   * </ul>
   *
   * @since 8.12
   */
  @StatelessCheck
  public class InterfaceMemberImpliedModifierCheck
      extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties" file.
       */
      public static final String MSG_KEY = "interface.implied.modifier";
  
      /** Name for 'public' access modifier. */
      private static final String PUBLIC_ACCESS_MODIFIER = "public";
  
      /** Name for 'abstract' keyword. */
      private static final String ABSTRACT_KEYWORD = "abstract";
  
      /** Name for 'static' keyword. */
      private static final String STATIC_KEYWORD = "static";
  
      /** Name for 'final' keyword. */
      private static final String FINAL_KEYWORD = "final";
  
      /**
       * Control whether to enforce that {@code public} is explicitly coded
       * on interface fields.
       */
      private boolean violateImpliedPublicField = true;
  
      /**
       * Control whether to enforce that {@code static} is explicitly coded
       * on interface fields.
       */
      private boolean violateImpliedStaticField = true;
  
      /**
       * Control whether to enforce that {@code final} is explicitly coded
       * on interface fields.
       */
      private boolean violateImpliedFinalField = true;
  
      /**
       * Control whether to enforce that {@code public} is explicitly coded
       * on interface methods.
       */
      private boolean violateImpliedPublicMethod = true;
  
      /**
       * Control whether to enforce that {@code abstract} is explicitly coded
       * on interface methods.
       */
      private boolean violateImpliedAbstractMethod = true;
  
      /**
       * Control whether to enforce that {@code public} is explicitly coded
       * on interface nested types.
       */
      private boolean violateImpliedPublicNested = true;
  
      /**
       * Control whether to enforce that {@code static} is explicitly coded
       * on interface nested types.
       */
      private boolean violateImpliedStaticNested = true;
  
      /**
       * Setter to control whether to enforce that {@code public} is explicitly coded
       * on interface fields.
       *
       * @param violateImpliedPublicField
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedPublicField(boolean violateImpliedPublicField) {
          this.violateImpliedPublicField = violateImpliedPublicField;
      }
  
      /**
       * Setter to control whether to enforce that {@code static} is explicitly coded
       * on interface fields.
       *
       * @param violateImpliedStaticField
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedStaticField(boolean violateImpliedStaticField) {
          this.violateImpliedStaticField = violateImpliedStaticField;
      }
  
      /**
       * Setter to control whether to enforce that {@code final} is explicitly coded
       * on interface fields.
       *
       * @param violateImpliedFinalField
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedFinalField(boolean violateImpliedFinalField) {
          this.violateImpliedFinalField = violateImpliedFinalField;
      }
  
      /**
       * Setter to control whether to enforce that {@code public} is explicitly coded
       * on interface methods.
       *
       * @param violateImpliedPublicMethod
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedPublicMethod(boolean violateImpliedPublicMethod) {
          this.violateImpliedPublicMethod = violateImpliedPublicMethod;
      }
  
      /**
       * Setter to control whether to enforce that {@code abstract} is explicitly coded
       * on interface methods.
       *
       * @param violateImpliedAbstractMethod
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedAbstractMethod(boolean violateImpliedAbstractMethod) {
          this.violateImpliedAbstractMethod = violateImpliedAbstractMethod;
      }
  
      /**
       * Setter to control whether to enforce that {@code public} is explicitly coded
       * on interface nested types.
       *
       * @param violateImpliedPublicNested
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedPublicNested(boolean violateImpliedPublicNested) {
          this.violateImpliedPublicNested = violateImpliedPublicNested;
      }
  
      /**
       * Setter to control whether to enforce that {@code static} is explicitly coded
       * on interface nested types.
       *
       * @param violateImpliedStaticNested
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedStaticNested(boolean violateImpliedStaticNested) {
          this.violateImpliedStaticNested = violateImpliedStaticNested;
      }
  
      @Override
      public int[] getDefaultTokens() {
          return getAcceptableTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return getAcceptableTokens();
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return new int[] {
              TokenTypes.METHOD_DEF,
              TokenTypes.VARIABLE_DEF,
              TokenTypes.INTERFACE_DEF,
              TokenTypes.CLASS_DEF,
              TokenTypes.ENUM_DEF,
          };
      }
  
      @Override
      public void visitToken(DetailAST ast) {
          if (ScopeUtil.isInInterfaceBlock(ast) && !ScopeUtil.isInCodeBlock(ast)) {
              switch (ast.getType()) {
                  case TokenTypes.METHOD_DEF:
                      processMethod(ast);
                      break;
                  case TokenTypes.VARIABLE_DEF:
                      processField(ast);
                      break;
                  case TokenTypes.CLASS_DEF:
                  case TokenTypes.INTERFACE_DEF:
                  case TokenTypes.ENUM_DEF:
                      processNestedType(ast);
                      break;
                  default:
                      throw new IllegalStateException(ast.toString());
              }
          }
      }
  
      /**
       * Check method in interface.
       *
       * @param ast the method AST
       */
      private void processMethod(DetailAST ast) {
          final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
          if (violateImpliedPublicMethod
                  && modifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) == null
                  && modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
              log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
          }
          if (violateImpliedAbstractMethod
                  && modifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) == null
                  && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null
                  && modifiers.findFirstToken(TokenTypes.LITERAL_DEFAULT) == null
                  && modifiers.findFirstToken(TokenTypes.ABSTRACT) == null) {
              log(ast, MSG_KEY, ABSTRACT_KEYWORD);
          }
      }
  
      /**
       * Check field in interface.
       *
       * @param ast the field AST
       */
      private void processField(DetailAST ast) {
          final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
          if (violateImpliedPublicField
                  && modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
              log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
          }
          if (violateImpliedStaticField
                  && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
              log(ast, MSG_KEY, STATIC_KEYWORD);
          }
          if (violateImpliedFinalField
                  && modifiers.findFirstToken(TokenTypes.FINAL) == null) {
              log(ast, MSG_KEY, FINAL_KEYWORD);
          }
      }
  
      /**
       * Check nested types in interface.
       *
       * @param ast the nested type AST
       */
      private void processNestedType(DetailAST ast) {
          final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
          if (violateImpliedPublicNested
                  && modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
              log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
          }
          if (violateImpliedStaticNested
                  && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
              log(ast, MSG_KEY, STATIC_KEYWORD);
          }
      }
  
  }
  