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.metrics;
  
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  
  /**
   * <p>
   * Checks the number of other types a given class/record/interface/enum/annotation
   * relies on. Also, the square of this has been shown to indicate the amount
   * of maintenance required in functional programs (on a file basis) at least.
   * </p>
   * <p>
   * This check processes files in the following way:
   * </p>
   * <ol>
   * <li>
   * Iterates over all tokens that might contain type reference.
   * </li>
   * <li>
   * If a class was imported with direct import (i.e. {@code import java.math.BigDecimal}),
   * or the class was referenced with the package name (i.e. {@code java.math.BigDecimal value})
   * and the package was added to the {@code excludedPackages} parameter,
   * the class does not increase complexity.
   * </li>
   * <li>
   * If a class name was added to the {@code excludedClasses} parameter,
   * the class does not increase complexity.
   * </li>
   * </ol>
   * <ul>
   * <li>
   * Property {@code max} - Specify the maximum threshold allowed.
   * Type is {@code int}.
   * Default value is {@code 20}.
   * </li>
   * <li>
   * Property {@code excludedClasses} - Specify user-configured class names to ignore.
   * Type is {@code java.lang.String[]}.
   * Default value is {@code ArrayIndexOutOfBoundsException, ArrayList, Boolean, Byte,
   * Character, Class, Collection, Deprecated, Deque, Double, DoubleStream, EnumSet, Exception,
   * Float, FunctionalInterface, HashMap, HashSet, IllegalArgumentException, IllegalStateException,
   * IndexOutOfBoundsException, IntStream, Integer, LinkedHashMap, LinkedHashSet, LinkedList, List,
   * Long, LongStream, Map, NullPointerException, Object, Optional, OptionalDouble, OptionalInt,
   * OptionalLong, Override, Queue, RuntimeException, SafeVarargs, SecurityException, Set, Short,
   * SortedMap, SortedSet, Stream, String, StringBuffer, StringBuilder, SuppressWarnings, Throwable,
   * TreeMap, TreeSet, UnsupportedOperationException, Void, boolean, byte, char, double,
   * float, int, long, short, var, void}.
   * </li>
   * <li>
   * Property {@code excludeClassesRegexps} - Specify user-configured regular
   * expressions to ignore classes.
   * Type is {@code java.util.regex.Pattern[]}.
   * Default value is {@code ^$}.
   * </li>
   * <li>
   * Property {@code excludedPackages} - Specify user-configured packages to ignore.
   * All excluded packages should end with a period, so it also appends a dot to a package name.
   * Type is {@code java.lang.String[]}.
   * Default value is {@code ""}.
   * </li>
   * </ul>
   * <p>
   * To configure the check:
   * </p>
   * <pre>
   * &lt;module name="ClassFanOutComplexity"/&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <p>
   * The check passes without violations in the following:
   * </p>
   * <pre>
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property
   *   Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property
   *   Date date = new Date(); // Counted, 1
   *   Time time = new Time(); // Counted, 2
   *   Place place = new Place(); // Counted, 3
   *   int value = 10; // int is ignored due to default excludedClasses property
   *   void method() {
   *     var result = "result"; // var is ignored due to default excludedClasses property
   *   }
   * }
   * </pre>
   * <p>
   * The check results in a violation in the following:
   * </p>
   * <pre>
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property
   *   Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property
   *   Date date = new Date(); // Counted, 1
   *   Time time = new Time(); // Counted, 2
   *   // mention of 18 other user defined classes
   *   Place place = new Place(); // violation, total is 21
   * }
   * </pre>
   * <p>
   * To configure the check with a threshold of 2:
   * </p>
   * <pre>
   * &lt;module name="ClassFanOutComplexity"&gt;
   *   &lt;property name="max" value="2"/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <p>
   * The check passes without violations in the following:
   * </p>
   * <pre>
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property
   *   Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property
   *   Date date = new Date(); // Counted, 1
   *   Time time = new Time(); // Counted, 2
   * }
   * </pre>
   * <p>
   * The check results in a violation in the following:
   * </p>
   * <pre>
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property
   *   Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property
   *   Date date = new Date(); // Counted, 1
   *   Time time = new Time(); // Counted, 2
   *   Place place = new Place(); // violation, total is 3
   * }
   * </pre>
   * <p>
   * To configure the check with three excluded classes {@code HashMap},
   * {@code HashSet} and {@code Place}:
   * </p>
   * <pre>
   * &lt;module name="ClassFanOutComplexity"&gt;
   *   &lt;property name="excludedClasses" value="HashMap, HashSet, Place"/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <p>
   * The check passes without violations in the following:
   * </p>
   * <pre>
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set counted 1, HashSet ignored
   *   Map map = new HashMap(); // Map counted 2, HashMap ignored
   *   Date date = new Date(); // Counted, 3
   *   Time time = new Time(); // Counted, 4
   *   // mention of 16 other user defined classes
   *   Place place = new Place(); // Ignored
   * }
   * </pre>
   * <p>
   * The check results in a violation in the following:
   * </p>
   * <pre>
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set counted 1, HashSet ignored
   *   Map map = new HashMap(); // Map counted 2, HashMap ignored
   *   Date date = new Date(); // Counted, 3
   *   Time time = new Time(); // Counted, 4
   *   // mention of 16 other user defined classes
   *   Space space = new Space(); // violation, total is 21
   * }
   * </pre>
   * <p>
   * To configure the check to exclude classes with a regular expression
   * {@code .*Reader$}:
   * </p>
   * <pre>
   * &lt;module name="ClassFanOutComplexity"&gt;
   *   &lt;property name="excludeClassesRegexps" value=".*Reader$"/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <p>
   * The check passes without violations in the following:
   * </p>
   * <pre>
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property
   *   Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property
   *   Date date = new Date(); // Counted, 1
   *   Time time = new Time(); // Counted, 2
   *   // mention of 18 other user defined classes
   *   BufferedReader br; // Ignored
   * }
   * </pre>
   * <p>
   * The check results in a violation in the following:
   * </p>
   * <pre>
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property
   *   Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property
   *   Date date = new Date(); // Counted, 1
   *   Time time = new Time(); // Counted, 2
   *   // mention of 18 other user defined classes
   *   File file; // violation, total is 21
   * }
   * </pre>
   * <p>
   * To configure the check with an excluded package {@code java.io}:
   * </p>
   * <pre>
   * &lt;module name="ClassFanOutComplexity"&gt;
   *   &lt;property name="excludedPackages" value="java.io"/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <p>
   * The check passes without violations in the following:
   * </p>
   * <pre>
   * import java.io.BufferedReader;
   *
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property
   *   Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property
   *   Date date = new Date(); // Counted, 1
   *   Time time = new Time(); // Counted, 2
   *   // mention of 18 other user defined classes
   *   BufferedReader br; // Ignored
   * }
   * </pre>
   * <p>
   * The check results in a violation in the following:
   * </p>
   * <pre>
   * import java.util.StringTokenizer;
   *
   * class InputClassComplexity {
   *   Set set = new HashSet(); // Set, HashSet ignored due to default excludedClasses property
   *   Map map = new HashMap(); // Map, HashMap ignored due to default excludedClasses property
   *   Date date = new Date(); // Counted, 1
   *   Time time = new Time(); // Counted, 2
   *   // mention of 18 other user defined classes
   *   StringTokenizer st; // violation, total is 21
   * }
   * </pre>
   * <p>
   * Override property {@code excludedPackages} to mark some packages as excluded.
   * Each member of {@code excludedPackages} should be a valid identifier:
   * </p>
   * <ul>
   * <li>
   * {@code java.util} - valid, excludes all classes inside {@code java.util},
   * but not from the subpackages.
   * </li>
   * <li>
   * {@code java.util.} - invalid, should not end with a dot.
   * </li>
   * <li>
   * {@code java.util.*} - invalid, should not end with a star.
   * </li>
   * </ul>
   * <p>
   * Note, that checkstyle will ignore all classes from the {@code java.lang}
   * package and its subpackages, even if the {@code java.lang} was not listed
   * in the {@code excludedPackages} parameter.
   * </p>
   * <p>
   * Also note, that {@code excludedPackages} will not exclude classes, imported
   * via wildcard (e.g. {@code import java.math.*}). Instead of wildcard import
   * you should use direct import (e.g. {@code import java.math.BigDecimal}).
   * </p>
   * <p>
   * Also note, that checkstyle will not exclude classes within the same file even
   * if it was listed in the {@code excludedPackages} parameter.
   * For example, assuming the config is
   * </p>
   * <pre>
   * &lt;module name="ClassFanOutComplexity"&gt;
   *   &lt;property name="excludedPackages" value="a.b"/&gt;
   * &lt;/module&gt;
   * </pre>
   * <p>
   * And the file {@code a.b.Foo.java} is:
   * </p>
   * <pre>
   * package a.b;
   *
   * import a.b.Bar;
   * import a.b.c.Baz;
   *
   * class Foo {
   *   Bar bar; // Will be ignored, located inside ignored a.b package
   *   Baz baz; // Will not be ignored, located inside a.b.c package
   *   Data data; // Will not be ignored, same file
   *
   *   class Data {
   *     Foo foo; // Will not be ignored, same file
   *   }
   * }
   * </pre>
   * <p>
   * The {@code bar} member will not be counted, since the {@code a.b}
   * added to the {@code excludedPackages}. The {@code baz} member will be counted,
   * since the {@code a.b.c} was not added to the {@code excludedPackages}.
   * The {@code data} and {@code foo} members will be counted, as they are inside same file.
   * </p>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code classFanOutComplexity}
   * </li>
   * </ul>
   *
   * @since 3.4
   */
  public final class ClassFanOutComplexityCheck extends AbstractClassCouplingCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "classFanOutComplexity";
  
      /** Default value of max value. */
      private static final int DEFAULT_MAX = 20;
  
      /** Creates new instance of this check. */
      public ClassFanOutComplexityCheck() {
          super(DEFAULT_MAX);
      }
  
      @Override
      public int[] getRequiredTokens() {
          return new int[] {
              TokenTypes.PACKAGE_DEF,
              TokenTypes.IMPORT,
              TokenTypes.CLASS_DEF,
              TokenTypes.EXTENDS_CLAUSE,
              TokenTypes.IMPLEMENTS_CLAUSE,
              TokenTypes.ANNOTATION,
              TokenTypes.INTERFACE_DEF,
              TokenTypes.ENUM_DEF,
              TokenTypes.TYPE,
              TokenTypes.LITERAL_NEW,
              TokenTypes.LITERAL_THROWS,
              TokenTypes.ANNOTATION_DEF,
              TokenTypes.RECORD_DEF,
          };
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return getRequiredTokens();
      }
  
      @Override
      protected String getLogMessageId() {
          return MSG_KEY;
      }
  
  }
  