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.sizes;
  
  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;
  
  /**
   * <p>
   * Checks lambda body length.
   * </p>
   * <p>
   * Rationale: Similar to anonymous inner classes, if lambda body becomes very long
   * it is hard to understand and to see the flow of the method
   * where the lambda is defined. Therefore, long lambda body
   * should usually be extracted to method.
   * </p>
   * <ul>
   * <li>
   * Property {@code max} - Specify the maximum number of lines allowed.
   * Type is {@code int}.
   * Default value is {@code 10}.
   * </li>
   * </ul>
   * <p>
   * To configure the check to accept lambda bodies with up to 10 lines:
   * </p>
   * <pre>
   * &lt;module name="LambdaBodyLength"/&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <pre>
   * class Test {
   *   Runnable r = () -&gt; { // violation, 11 lines
   *       System.out.println(2); // line 2 of lambda
   *       System.out.println(3);
   *       System.out.println(4);
   *       System.out.println(5);
   *       System.out.println(6);
   *       System.out.println(7);
   *       System.out.println(8);
   *       System.out.println(9);
   *       System.out.println(10);
   *   }; // line 11
   *
   *   Runnable r2 = () -&gt; // violation, 11 lines
   *       "someString".concat("1") // line 1 of lambda
   *                   .concat("2")
   *                   .concat("3")
   *                   .concat("4")
   *                   .concat("5")
   *                   .concat("6")
   *                   .concat("7")
   *                   .concat("8")
   *                   .concat("9")
   *                   .concat("10")
   *                   .concat("11"); // line 11
   *
   *   Runnable r3 = () -&gt; { // ok, 10 lines
   *       System.out.println(2); // line 2 of lambda
   *       System.out.println(3);
   *       System.out.println(4);
   *       System.out.println(5);
   *       System.out.println(6);
   *       System.out.println(7);
   *       System.out.println(8);
   *       System.out.println(9);
   *   }; // line 10
   * }
   * </pre>
   * <p>
   * To configure the check to accept lambda bodies with max 5 lines:
   * </p>
   * <pre>
   * &lt;module name="LambdaBodyLength"&gt;
   *   &lt;property name="max" value="5"/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <pre>
   * class Test {
   *   Runnable r = () -&gt; { // violation, 6 lines
   *       System.out.println(2); // line 2 of lambda
   *       System.out.println(3);
   *       System.out.println(4);
   *       System.out.println(5);
   *   };
   *
   *   Runnable r2 = () -&gt; // violation, 6 lines
   *       "someString".concat("1")
   *                   .concat("2")
   *                   .concat("3")
   *                   .concat("4")
   *                   .concat("5")
   *                   .concat("6");
   *
   *   Runnable r3 = () -&gt; { // ok, 5 lines
   *       System.out.println(2);
   *       System.out.println(3);
   *       System.out.println(4);
   *   };
   * }
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code maxLen.lambdaBody}
   * </li>
   * </ul>
   *
   * @since 8.37
   */
  @StatelessCheck
  public class LambdaBodyLengthCheck extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "maxLen.lambdaBody";
  
      /** Default maximum number of lines. */
      private static final int DEFAULT_MAX = 10;
  
      /** Specify the maximum number of lines allowed. */
      private int max = DEFAULT_MAX;
  
      /**
       * Setter to specify the maximum number of lines allowed.
       *
       * @param length the maximum length of lambda body.
       */
      public void setMax(int length) {
          max = length;
      }
  
      @Override
      public int[] getDefaultTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return getRequiredTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return new int[] {TokenTypes.LAMBDA};
      }
  
      @Override
      public void visitToken(DetailAST ast) {
          if (ast.getParent().getType() != TokenTypes.SWITCH_RULE) {
              final int length = getLength(ast);
              if (length > max) {
                  log(ast, MSG_KEY, length, max);
              }
          }
      }
  
      /**
       * Get length of lambda body.
       *
       * @param ast lambda body node.
       * @return length of lambda body.
       */
      private static int getLength(DetailAST ast) {
          final DetailAST lambdaBody = ast.getLastChild();
          final int length;
          if (lambdaBody.getType() == TokenTypes.SLIST) {
              length = lambdaBody.getLastChild().getLineNo() - lambdaBody.getLineNo();
          }
          else {
              length = getLastNodeLineNumber(lambdaBody) - getFirstNodeLineNumber(lambdaBody);
          }
          return length + 1;
      }
  
      /**
       * Get last child node in the tree line number.
       *
       * @param lambdaBody lambda body node.
       * @return last child node in the tree line number.
       */
      private static int getLastNodeLineNumber(DetailAST lambdaBody) {
          DetailAST node = lambdaBody;
          int result;
          do {
              result = node.getLineNo();
              node = node.getLastChild();
          } while (node != null);
          return result;
      }
  
      /**
       * Get first child node in the tree line number.
       *
       * @param lambdaBody lambda body node.
       * @return first child node in the tree line number.
       */
      private static int getFirstNodeLineNumber(DetailAST lambdaBody) {
          DetailAST node = lambdaBody;
          int result;
          do {
              result = node.getLineNo();
              node = node.getFirstChild();
          } while (node != null);
          return result;
      }
  
  }
  