ClassFanOutComplexityCheck.java
////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2021 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.lang.String[]}.
* Validation 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>
* <module name="ClassFanOutComplexity"/>
* </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>
* <module name="ClassFanOutComplexity">
* <property name="max" value="2"/>
* </module>
* </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>
* <module name="ClassFanOutComplexity">
* <property name="excludedClasses" value="HashMap, HashSet, Place"/>
* </module>
* </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>
* <module name="ClassFanOutComplexity">
* <property name="excludeClassesRegexps" value=".*Reader$"/>
* </module>
* </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>
* <module name="ClassFanOutComplexity">
* <property name="excludedPackages" value="java.io"/>
* </module>
* </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>
* <module name="ClassFanOutComplexity">
* <property name="excludedPackages" value="a.b"/>
* </module>
* </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;
}
}