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.regexp;
  
  import java.io.File;
  import java.util.regex.Pattern;
  
  import com.puppycrawl.tools.checkstyle.PropertyType;
  import com.puppycrawl.tools.checkstyle.StatelessCheck;
  import com.puppycrawl.tools.checkstyle.XdocsPropertyType;
  import com.puppycrawl.tools.checkstyle.api.AbstractFileSetCheck;
  import com.puppycrawl.tools.checkstyle.api.FileText;
  
  /**
   * <p>
   * Checks that a specified pattern matches across multiple lines in any file type.
   * </p>
   * <p>
   * Rationale: This check can be used to when the regular expression can be span multiple lines.
   * </p>
   * <ul>
   * <li>
   * Property {@code format} - Specify the format of the regular expression to match.
   * Type is {@code java.util.regex.Pattern}.
   * Default value is {@code "$."}.
   * </li>
   * <li>
   * Property {@code message} - Specify the message which is used to notify about
   * violations, if empty then default (hard-coded) message is used.
   * Type is {@code java.lang.String}.
   * Default value is {@code null}.
   * </li>
   * <li>
   * Property {@code ignoreCase} - Control whether to ignore case when searching.
   * Type is {@code boolean}.
   * Default value is {@code false}.
   * </li>
   * <li>
   * Property {@code minimum} - Specify the minimum number of matches required in each file.
   * Type is {@code int}.
   * Default value is {@code 0}.
   * </li>
   * <li>
   * Property {@code maximum} - Specify the maximum number of matches required in each file.
   * Type is {@code int}.
   * Default value is {@code 0}.
   * </li>
   * <li>
   * Property {@code matchAcrossLines} - Control whether to match expressions
   * across multiple lines.
   * Type is {@code boolean}.
   * Default value is {@code false}.
   * </li>
   * <li>
   * Property {@code fileExtensions} - Specify the file type extension of files to process.
   * Type is {@code java.lang.String[]}.
   * Default value is {@code ""}.
   * </li>
   * </ul>
   * <p>
   * To run the check with its default configuration (no matches will be):
   * </p>
   * <pre>
   * &lt;module name=&quot;RegexpMultiline&quot;/&gt;
   * </pre>
   * <p>Example: </p>
   * <pre>
   * void method() {
   *   int i = 5; // OK
   *   System.out.println(i); // OK
   * }
   * </pre>
   * <p>
   * To configure the check to find calls to print to the console:
   * </p>
   * <pre>
   * &lt;module name="RegexpMultiline"&gt;
   *   &lt;property name="format" value="System\.(out)|(err)\.print(ln)?\("/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <pre>
   * void method() {
   *   System.out.print("Example");   // violation
   *   System.err.println("Example"); // violation
   *   System.out.print
   *     ("Example");                 // violation
   *   System.err.println
   *     ("Example");          // OK
   *   System
   *   .out.print("Example");  // OK
   *   System
   *   .err.println("Example");       // violation
   *   System.
   *   out.print("Example");   // OK
   *   System.
   *   err.println("Example");        // violation
   * }
   * </pre>
   * <p>
   * To configure the check to match text that spans multiple lines,
   * like normal code in a Java file:
   * </p>
   * <pre>
   * &lt;module name="RegexpMultiline"&gt;
   *   &lt;property name="matchAcrossLines" value="true"/&gt;
   *   &lt;property name="format" value="System\.out.*?print\("/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <pre>
   * void method() {
   *   System.out.print("Example");  // violation
   *   System.err.println("Example");
   *   System.out.print              // violation
   *     ("Example");
   *   System.err.println
   *     ("Example");
   *   System
   *   .out.print("Example");
   *   System
   *   .err.println("Example");
   *   System.
   *   out.print("Example");
   *   System.
   *   err.println("Example");
   * }
   * </pre>
   * <p>
   * Note: Beware of the greedy regular expression used in the above example.
   * {@code .*} will match as much as possible and not produce multiple violations
   * in the file if multiple groups of lines could match the expression. To prevent
   * an expression being too greedy, avoid overusing matching all text or allow it
   * to be optional, like {@code .*?}. Changing the example expression to not be
   * greedy will allow multiple violations in the example to be found in the same file.
   * </p>
   * <p>
   * To configure the check to match a maximum of three test strings:
   * </p>
   * <pre>
   * &lt;module name=&quot;RegexpMultiline&quot;&gt;
   *   &lt;property name=&quot;format&quot; value=&quot;Test #[0-9]+:[A-Za-z ]+&quot;/&gt;
   *   &lt;property name=&quot;ignoreCase&quot; value=&quot;true&quot;/&gt;
   *   &lt;property name=&quot;maximum&quot; value=&quot;3&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <pre>
   * void method() {
   *   System.out.println("Test #1: this is a test string"); // OK
   *   System.out.println("TeSt #2: This is a test string"); // OK
   *   System.out.println("TEST #3: This is a test string"); // OK
   *   int i = 5;
   *   System.out.println("Value of i: " + i);
   *   System.out.println("Test #4: This is a test string"); // violation
   *   System.out.println("TEst #5: This is a test string"); // violation
   * }
   * </pre>
   * <p>
   * To configure the check to match a minimum of two test strings:
   * </p>
   * <pre>
   * &lt;module name=&quot;RegexpMultiline&quot;&gt;
   *   &lt;property name=&quot;format&quot; value=&quot;Test #[0-9]+:[A-Za-z ]+&quot;/&gt;
   *   &lt;property name=&quot;minimum&quot; value=&quot;2&quot;/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <pre>
   * void method() {
   *   System.out.println("Test #1: this is a test string"); // violation
   *   System.out.println("TEST #2: This is a test string"); // OK, "ignoreCase" is false by default
   *   int i = 5;
   *   System.out.println("Value of i: " + i);
   *   System.out.println("Test #3: This is a test string"); // violation
   *   System.out.println("Test #4: This is a test string"); // violation
   * }
   * </pre>
   * <p>
   * To configure the check to restrict an empty file:
   * </p>
   * <pre>
   * &lt;module name=&quot;RegexpMultiline&quot;&gt;
   *     &lt;property name=&quot;format&quot; value=&quot;^\s*$&quot; /&gt;
   *     &lt;property name=&quot;matchAcrossLines&quot; value=&quot;true&quot; /&gt;
   *     &lt;property name=&quot;message&quot; value=&quot;Empty file is not allowed&quot; /&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example of violation from the above config:
   * </p>
   * <pre>
   * /var/tmp$ cat -n Test.java
   * 1
   * 2
   * 3
   * 4
   * </pre>
   * <p>Result:</p>
   * <pre>
   * /var/tmp/Test.java // violation, a file must not be empty.
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.Checker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code regexp.StackOverflowError}
   * </li>
   * <li>
   * {@code regexp.empty}
   * </li>
   * <li>
   * {@code regexp.exceeded}
   * </li>
   * <li>
   * {@code regexp.minimum}
   * </li>
   * </ul>
   *
   * @since 5.0
   */
  @StatelessCheck
  public class RegexpMultilineCheck extends AbstractFileSetCheck {
  
      /** Specify the format of the regular expression to match. */
      @XdocsPropertyType(PropertyType.PATTERN)
      private String format = "$.";
      /**
       * Specify the message which is used to notify about violations,
       * if empty then default (hard-coded) message is used.
       */
      private String message;
      /** Specify the minimum number of matches required in each file. */
      private int minimum;
      /** Specify the maximum number of matches required in each file. */
      private int maximum;
      /** Control whether to ignore case when searching. */
      private boolean ignoreCase;
      /** Control whether to match expressions across multiple lines. */
      private boolean matchAcrossLines;
  
      /** The detector to use. */
      private MultilineDetector detector;
  
      @Override
      public void beginProcessing(String charset) {
          final DetectorOptions options = DetectorOptions.newBuilder()
              .reporter(this)
              .compileFlags(getRegexCompileFlags())
              .format(format)
              .message(message)
              .minimum(minimum)
              .maximum(maximum)
              .ignoreCase(ignoreCase)
              .build();
          detector = new MultilineDetector(options);
      }
  
      @Override
      protected void processFiltered(File file, FileText fileText) {
          detector.processLines(fileText);
      }
  
      /**
       * Retrieves the compile-flags for the regular expression being built based
       * on {@code matchAcrossLines}.
       *
       * @return The compile-flags.
       */
      private int getRegexCompileFlags() {
          final int result;
  
          if (matchAcrossLines) {
              result = Pattern.DOTALL;
          }
          else {
              result = Pattern.MULTILINE;
          }
  
          return result;
      }
  
      /**
       * Setter to specify the format of the regular expression to match.
       *
       * @param format the format of the regular expression to match.
       */
      public void setFormat(String format) {
          this.format = format;
      }
  
      /**
       * Setter to specify the message which is used to notify about violations,
       * if empty then default (hard-coded) message is used.
       *
       * @param message the message to report for a match.
       */
      public void setMessage(String message) {
          this.message = message;
      }
  
      /**
       * Setter to specify the minimum number of matches required in each file.
       *
       * @param minimum the minimum number of matches required in each file.
       */
      public void setMinimum(int minimum) {
          this.minimum = minimum;
      }
  
      /**
       * Setter to specify the maximum number of matches required in each file.
       *
       * @param maximum the maximum number of matches required in each file.
       */
      public void setMaximum(int maximum) {
          this.maximum = maximum;
      }
  
      /**
       * Setter to control whether to ignore case when searching.
       *
       * @param ignoreCase whether to ignore case when searching.
       */
      public void setIgnoreCase(boolean ignoreCase) {
          this.ignoreCase = ignoreCase;
      }
  
      /**
       * Setter to control whether to match expressions across multiple lines.
       *
       * @param matchAcrossLines whether to match expressions across multiple lines.
       */
      public void setMatchAcrossLines(boolean matchAcrossLines) {
          this.matchAcrossLines = matchAcrossLines;
      }
  
  }
  