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.naming;
  
  import java.util.Arrays;
  import java.util.Optional;
  
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.CheckUtil;
  
  /**
   * <p>
   * Checks that method parameter names conform to a specified pattern.
   * By using {@code accessModifiers} property it is possible
   * to specify different formats for methods at different visibility levels.
   * </p>
   * <p>
   * To validate {@code catch} parameters please use
   * <a href="https://checkstyle.org/checks/naming/catchparametername.html#CatchParameterName">
   * CatchParameterName</a>.
   * </p>
   * <p>
   * To validate lambda parameters please use
   * <a href="https://checkstyle.org/checks/naming/lambdaparametername.html#LambdaParameterName">
   * LambdaParameterName</a>.
   * </p>
   * <ul>
   * <li>
   * Property {@code format} - Specifies valid identifiers.
   * Type is {@code java.util.regex.Pattern}.
   * Default value is {@code "^[a-z][a-zA-Z0-9]*$"}.
   * </li>
   * <li>
   * Property {@code ignoreOverridden} - Allows to skip methods with Override annotation from
   * validation.
   * Type is {@code boolean}.
   * Default value is {@code false}.
   * </li>
   * <li>
   * Property {@code accessModifiers} - Access modifiers of methods where parameters are
   * checked.
   * Type is {@code com.puppycrawl.tools.checkstyle.checks.naming.AccessModifierOption[]}.
   * Default value is {@code public, protected, package, private}.
   * </li>
   * </ul>
   * <p>
   * To configure the check:
   * </p>
   * <pre>
   * &lt;module name=&quot;ParameterName&quot;/&gt;
   * </pre>
   * <p>Code Example:</p>
   * <pre>
   * class MyClass {
   *   void method1(int v1) {} // OK
   *   void method2(int V2) {} // violation, name 'V2' must match pattern '^[a-z][a-zA-Z0-9]*$'
   * }
   * </pre>
   * <p>
   * An example of how to configure the check for names that begin with
   * a lower case letter, followed by letters, digits, and underscores:
   * </p>
   * <pre>
   * &lt;module name=&quot;ParameterName&quot;&gt;
   *   &lt;property name=&quot;format&quot; value=&quot;^[a-z][_a-zA-Z0-9]+$&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Code Example:</p>
   * <pre>
   * class MyClass {
   *   void method1(int v1) {} // OK
   *   void method2(int v_2) {} // OK
   *   void method3(int V3) {} // violation, name 'V3' must match pattern '^[a-z][_a-zA-Z0-9]+$'
   * }
   * </pre>
   * <p>
   * An example of how to configure the check to skip methods with Override annotation from
   * validation:
   * </p>
   * <pre>
   * &lt;module name=&quot;ParameterName&quot;&gt;
   *   &lt;property name=&quot;ignoreOverridden&quot; value=&quot;true&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Code Example:</p>
   * <pre>
   * class MyClass {
   *   void method1(int v1) {} // OK
   *   void method2(int V2) {} // violation, name 'V2' must match pattern '^[a-z][a-zA-Z0-9]*$'
   *   &#064;Override
   *   public boolean equals(Object V3) { // OK
   *       return true;
   *   }
   * }
   * </pre>
   * <p>
   * An example of how to configure the check for names that begin with a lower case letter, followed
   * by letters and digits is:
   * </p>
   * <pre>
   * &lt;module name=&quot;ParameterName&quot;&gt;
   *   &lt;property name=&quot;format&quot; value=&quot;^[a-z][a-zA-Z0-9]+$&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Code Example:</p>
   * <pre>
   * class MyClass {
   *   void method1(int v1) {} // OK
   *   void method2(int v_2) {} // violation, name 'v_2' must match pattern '^[a-z][a-zA-Z0-9]+$'
   *   void method3(int V3) {} // violation, name 'V3' must match pattern '^[a-z][a-zA-Z0-9]+$'
   * }
   * </pre>
   * <p>
   * The following configuration checks that the parameters always start with two lowercase
   * characters and, in addition, that public method parameters cannot be one character long:
   * </p>
   * <pre>
   * &lt;module name=&quot;ParameterName&quot;&gt;
   *   &lt;property name=&quot;format&quot; value=&quot;^[a-z]([a-z0-9][a-zA-Z0-9]*)?$&quot;/&gt;
   *   &lt;property name=&quot;accessModifiers&quot;
   *     value=&quot;protected, package, private&quot;/&gt;
   *   &lt;message key=&quot;name.invalidPattern&quot;
   *     value=&quot;Parameter name ''{0}'' must match pattern ''{1}''&quot;/&gt;
   * &lt;/module&gt;
   * &lt;module name=&quot;ParameterName&quot;&gt;
   *   &lt;property name=&quot;format&quot; value=&quot;^[a-z][a-z0-9][a-zA-Z0-9]*$&quot;/&gt;
   *   &lt;property name=&quot;accessModifiers&quot; value=&quot;public&quot;/&gt;
   *   &lt;message key=&quot;name.invalidPattern&quot;
   *     value=&quot;Parameter name ''{0}'' must match pattern ''{1}''&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>Code Example:</p>
   * <pre>
   * class MyClass {
   *   void method1(int v1) {} // OK
   *   protected method2(int V2) {} // violation, Parameter name 'V2'
   *                                // must match pattern '^[a-z]([a-z0-9][a-zA-Z0-9]*)?$'
   *   private method3(int a) {} // OK
   *   public method4(int b) {} // violation, Parameter name 'b'
   *                            // must match pattern '^[a-z][a-z0-9][a-zA-Z0-9]*$'
   * }
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code name.invalidPattern}
   * </li>
   * </ul>
   *
   * @since 3.0
   */
  public class ParameterNameCheck extends AbstractNameCheck {
  
      /**
       * Allows to skip methods with Override annotation from validation.
       */
      private boolean ignoreOverridden;
  
      /** Access modifiers of methods where parameters are checked. */
      private AccessModifierOption[] accessModifiers = {
          AccessModifierOption.PUBLIC,
          AccessModifierOption.PROTECTED,
          AccessModifierOption.PACKAGE,
          AccessModifierOption.PRIVATE,
      };
  
      /**
       * Creates a new {@code ParameterNameCheck} instance.
       */
      public ParameterNameCheck() {
          super("^[a-z][a-zA-Z0-9]*$");
      }
  
      /**
       * Setter to allows to skip methods with Override annotation from validation.
       *
       * @param ignoreOverridden Flag for skipping methods with Override annotation.
       */
      public void setIgnoreOverridden(boolean ignoreOverridden) {
          this.ignoreOverridden = ignoreOverridden;
      }
  
      /**
       * Setter to access modifiers of methods where parameters are checked.
       *
       * @param accessModifiers access modifiers of methods which should be checked.
       */
      public void setAccessModifiers(AccessModifierOption... accessModifiers) {
          this.accessModifiers =
              Arrays.copyOf(accessModifiers, accessModifiers.length);
      }
  
      @Override
      public int[] getDefaultTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return new int[] {TokenTypes.PARAMETER_DEF};
      }
  
      @Override
      protected boolean mustCheckName(DetailAST ast) {
          boolean checkName = true;
          final DetailAST parent = ast.getParent();
          if (ignoreOverridden && isOverriddenMethod(ast)
                  || parent.getType() == TokenTypes.LITERAL_CATCH
                  || parent.getParent().getType() == TokenTypes.LAMBDA
                  || CheckUtil.isReceiverParameter(ast)
                  || !matchAccessModifiers(
                          CheckUtil.getAccessModifierFromModifiersToken(parent.getParent()))) {
              checkName = false;
          }
          return checkName;
      }
  
      /**
       * Checks whether a method has the correct access modifier to be checked.
       *
       * @param accessModifier the access modifier of the method.
       * @return whether the method matches the expected access modifier.
       */
      private boolean matchAccessModifiers(final AccessModifierOption accessModifier) {
          return Arrays.stream(accessModifiers)
                  .anyMatch(modifier -> modifier == accessModifier);
      }
  
      /**
       * Checks whether a method is annotated with Override annotation.
       *
       * @param ast method parameter definition token.
       * @return true if a method is annotated with Override annotation.
       */
      private static boolean isOverriddenMethod(DetailAST ast) {
          boolean overridden = false;
  
          final DetailAST parent = ast.getParent().getParent();
          final Optional<DetailAST> annotation =
              Optional.ofNullable(parent.getFirstChild().getFirstChild());
  
          if (annotation.isPresent()) {
              final Optional<DetailAST> overrideToken =
                  Optional.ofNullable(annotation.get().findFirstToken(TokenTypes.IDENT));
              if (overrideToken.isPresent() && "Override".equals(overrideToken.get().getText())) {
                  overridden = true;
              }
          }
          return overridden;
      }
  
  }
  