Source code

001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2022 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
018////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.checks.coding;
021
022import java.util.Collections;
023import java.util.HashSet;
024import java.util.List;
025import java.util.Set;
026import java.util.regex.Pattern;
027import java.util.stream.Collectors;
028import java.util.stream.Stream;
029
030import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
031import com.puppycrawl.tools.checkstyle.PropertyType;
032import com.puppycrawl.tools.checkstyle.XdocsPropertyType;
033import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
034import com.puppycrawl.tools.checkstyle.api.DetailAST;
035import com.puppycrawl.tools.checkstyle.api.FullIdent;
036import com.puppycrawl.tools.checkstyle.api.TokenTypes;
037import com.puppycrawl.tools.checkstyle.utils.AnnotationUtil;
038import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
039
040/**
041 * <p>
042 * Checks that particular classes or interfaces are never used.
043 * </p>
044 * <p>
045 * Rationale: Helps reduce coupling on concrete classes.
046 * </p>
047 * <p>
048 * For additional restriction of type usage see also:
049 * <a href="https://checkstyle.org/config_coding.html#IllegalInstantiation">
050 * IllegalInstantiation</a>,
051 * <a href="https://checkstyle.org/config_imports.html#IllegalImport">IllegalImport</a>
052 * </p>
053 * <p>
054 * It is possible to set illegal class names via short or
055 * <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-6.html#jls-6.7">canonical</a>
056 * name. Specifying illegal type invokes analyzing imports and Check puts violations at
057 * corresponding declarations (of variables, methods or parameters).
058 * This helps to avoid ambiguous cases, e.g.: {@code java.awt.List} was set as
059 * illegal class name, then, code like:
060 * </p>
061 * <pre>
062 * import java.util.List;
063 * ...
064 * List list; //No violation here
065 * </pre>
066 * <p>
067 * will be ok.
068 * </p>
069 * <p>
070 * In most cases it's justified to put following classes to <b>illegalClassNames</b>:
071 * </p>
072 * <ul>
073 * <li>GregorianCalendar</li>
074 * <li>Hashtable</li>
075 * <li>ArrayList</li>
076 * <li>LinkedList</li>
077 * <li>Vector</li>
078 * </ul>
079 * <p>
080 * as methods that are differ from interface methods are rarely used, so in most cases user will
081 * benefit from checking for them.
082 * </p>
083 * <ul>
084 * <li>
085 * Property {@code validateAbstractClassNames} - Control whether to validate abstract class names.
086 * Type is {@code boolean}.
087 * Default value is {@code false}.
088 * </li>
089 * <li>
090 * Property {@code illegalClassNames} - Specify classes that should not be used
091 * as types in variable declarations, return values or parameters.
092 * Type is {@code java.lang.String[]}.
093 * Default value is {@code HashMap, HashSet, LinkedHashMap, LinkedHashSet, TreeMap,
094 * TreeSet, java.util.HashMap, java.util.HashSet, java.util.LinkedHashMap,
095 * java.util.LinkedHashSet, java.util.TreeMap, java.util.TreeSet}.
096 * </li>
097 * <li>
098 * Property {@code legalAbstractClassNames} - Define abstract classes that may be used as types.
099 * Type is {@code java.lang.String[]}.
100 * Default value is {@code ""}.
101 * </li>
102 * <li>
103 * Property {@code ignoredMethodNames} - Specify methods that should not be checked.
104 * Type is {@code java.lang.String[]}.
105 * Default value is {@code getEnvironment, getInitialContext}.
106 * </li>
107 * <li>
108 * Property {@code illegalAbstractClassNameFormat} - Specify RegExp for illegal abstract class
109 * names.
110 * Type is {@code java.util.regex.Pattern}.
111 * Default value is {@code "^(.*[.])?Abstract.*$"}.
112 * </li>
113 * <li>
114 * Property {@code memberModifiers} - Control whether to check only methods and fields with any
115 * of the specified modifiers.
116 * This property does not affect method calls nor method references nor record components.
117 * Type is {@code java.lang.String[]}.
118 * Validation type is {@code tokenTypesSet}.
119 * Default value is {@code ""}.
120 * </li>
121 * <li>
122 * Property {@code tokens} - tokens to check
123 * Type is {@code java.lang.String[]}.
124 * Validation type is {@code tokenSet}.
125 * Default value is:
126 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ANNOTATION_FIELD_DEF">
127 * ANNOTATION_FIELD_DEF</a>,
128 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CLASS_DEF">
129 * CLASS_DEF</a>,
130 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#INTERFACE_DEF">
131 * INTERFACE_DEF</a>,
132 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_CALL">
133 * METHOD_CALL</a>,
134 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_DEF">
135 * METHOD_DEF</a>,
136 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_REF">
137 * METHOD_REF</a>,
138 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#PARAMETER_DEF">
139 * PARAMETER_DEF</a>,
140 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#VARIABLE_DEF">
141 * VARIABLE_DEF</a>,
142 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#PATTERN_VARIABLE_DEF">
143 * PATTERN_VARIABLE_DEF</a>,
144 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#RECORD_DEF">
145 * RECORD_DEF</a>,
146 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#RECORD_COMPONENT_DEF">
147 * RECORD_COMPONENT_DEF</a>.
148 * </li>
149 * </ul>
150 * <p>
151 * To configure the default check:
152 * </p>
153 * <pre>
154 * &lt;module name=&quot;IllegalType&quot;/&gt;
155 * </pre>
156 * <pre>
157 * public class Test extends TreeSet { // violation
158 *   public &lt;T extends java.util.HashSet&gt; void method() { // violation
159 *
160 *     LinkedHashMap&lt;Integer, String&gt; lhmap =
161 *     new LinkedHashMap&lt;Integer, String&gt;(); // violation
162 *     TreeMap&lt;Integer, String&gt; treemap =
163 *     new TreeMap&lt;Integer, String&gt;(); // violation
164 *     Test t; // OK
165 *     HashMap&lt;String, String&gt; hmap; // violation
166 *     Queue&lt;Integer&gt; intqueue; // OK
167 *
168 *     java.lang.IllegalArgumentException illegalex; // OK
169 *     java.util.TreeSet treeset; // violation
170 *   }
171 *
172 * }
173 * </pre>
174 * <p>
175 * To configure the Check so that particular tokens are checked:
176 * </p>
177 * <pre>
178 * &lt;module name="IllegalType"&gt;
179 *   &lt;property name="tokens" value="METHOD_DEF"/&gt;
180 * &lt;/module&gt;
181 * </pre>
182 * <pre>
183 * public class Test extends TreeSet { // OK
184 *   public &lt;T extends java.util.HashSet&gt; void method() { // violation
185 *     LinkedHashMap&lt;Integer, String&gt; lhmap =
186 *     new LinkedHashMap&lt;Integer, String&gt;(); // OK
187 *
188 *     java.lang.IllegalArgumentException illegalex; // OK
189 *     java.util.TreeSet treeset; // Ok
190 *   }
191 *
192 *   public &lt;T extends java.util.HashSet&gt; void typeParam(T t) {} // violation
193 *
194 *   public void fullName(TreeSet a) {} // OK
195 *
196 * }
197 * </pre>
198 * <p>
199 * To configure the Check so that it ignores function() methods:
200 * </p>
201 * <pre>
202 * &lt;module name=&quot;IllegalType&quot;&gt;
203 *   &lt;property name=&quot;ignoredMethodNames&quot; value=&quot;function&quot;/&gt;
204 * &lt;/module&gt;
205 * </pre>
206 * <pre>
207 * public class Test {
208 *   public HashMap&lt;String, String&gt; function() { // OK
209 *     // code
210 *   }
211 *
212 *   public HashMap&lt;String, String&gt; function1() { // violation
213 *     // code
214 *   }
215 * }
216 * </pre>
217 * <p>
218 * To configure the Check so that it validates abstract class names:
219 * </p>
220 * <pre>
221 *  &lt;module name=&quot;IllegalType&quot;&gt;
222 *    &lt;property name=&quot;validateAbstractClassNames&quot; value=&quot;true&quot;/&gt;
223 *    &lt;property name=&quot;illegalAbstractClassNameFormat&quot; value=&quot;Gitt&quot;/&gt;
224 *  &lt;/module&gt;
225 * </pre>
226 * <pre>
227 * class Test extends Gitter { // violation
228 * }
229 *
230 * class Test1 extends Github { // OK
231 * }
232 * </pre>
233 * <p>
234 * To configure the Check so that it verifies only public, protected or static methods and fields:
235 * </p>
236 * <pre>
237 * &lt;module name=&quot;IllegalType&quot;&gt;
238 *   &lt;property name=&quot;memberModifiers&quot; value=&quot;LITERAL_PUBLIC,
239 *    LITERAL_PROTECTED, LITERAL_STATIC&quot;/&gt;
240 * &lt;/module&gt;
241 * </pre>
242 * <pre>
243 * public class Test {
244 *   public HashMap&lt;String, String&gt; function1() { // violation
245 *     // code
246 *   }
247 *
248 *   private HashMap&lt;String, String&gt; function2() { // OK
249 *     // code
250 *   }
251 *
252 *   protected HashMap&lt;Integer, String&gt; function3() { // violation
253 *     // code
254 *   }
255 *
256 *   public static TreeMap&lt;Integer, String&gt; function4() { // violation
257 *     // code
258 *   }
259 *
260 * }
261 * </pre>
262 * <p>
263 * To configure the check so that it verifies usage of types Boolean and Foo:
264 * </p>
265 * <pre>
266 * &lt;module name=&quot;IllegalType&quot;&gt;
267 *           &lt;property name=&quot;illegalClassNames&quot; value=&quot;Boolean, Foo&quot;/&gt;
268 * &lt;/module&gt;
269 * </pre>
270 * <pre>
271 * public class Test {
272 *
273 *   public Set&lt;Boolean&gt; set; // violation
274 *   public java.util.List&lt;Map&lt;Boolean, Foo&gt;&gt; list; // violation
275 *
276 *   private void method(List&lt;Foo&gt; list, Boolean value) { // violation
277 *     SomeType.&lt;Boolean&gt;foo(); // violation
278 *     final Consumer&lt;Foo&gt; consumer = Foo&lt;Boolean&gt;::foo; // violation
279 *   }
280 *
281 *   public &lt;T extends Boolean, U extends Serializable&gt; void typeParam(T a) {} // violation
282 *
283 *   public void fullName(java.util.ArrayList&lt;? super Boolean&gt; a) {} // violation
284 *
285 *   public abstract Set&lt;Boolean&gt; shortName(Set&lt;? super Boolean&gt; a); // violation
286 *
287 *   public Set&lt;? extends Foo&gt; typeArgument() { // violation
288 *     return new TreeSet&lt;Foo&lt;Boolean&gt;&gt;();
289 *   }
290 *
291 * }
292 * </pre>
293 * <p>
294 * To configure the check to target fields types only:
295 * </p>
296 * <pre>
297 * &lt;module name="IllegalType"&gt;
298 *   &lt;property name=&quot;illegalClassNames&quot; value=&quot;java.util.Optional&quot;/&gt;
299 *   &lt;property name=&quot;tokens&quot; value=&quot;VARIABLE_DEF&quot;/&gt;
300 *   &lt;property name=&quot;id&quot; value=&quot;IllegalTypeOptionalAsField&quot;/&gt;
301 * &lt;/module&gt;
302 * &lt;module name="SuppressionXpathSingleFilter"&gt;
303 *   &lt;property name=&quot;query&quot; value=&quot;//METHOD_DEF//*&quot;/&gt;
304 *   &lt;property name=&quot;id&quot; value=&quot;IllegalTypeOptionalAsField&quot;/&gt;
305 * &lt;/module&gt;
306 * </pre>
307 * <pre>
308 * import java.util.Optional;
309 *
310 * public class Main {
311 *
312 *   static int field1 = 4; // OK
313 *   public Optional&lt;String&gt; field2; // violation, usage of type 'Optional' is not allowed
314 *   protected String field3; // OK
315 *   Optional&lt;String&gt; field4; // violation, usage of type 'Optional' is not allowed
316 *   private Optional&lt;String&gt; field5; // violation, usage of type 'Optional' is not allowed
317 *
318 *   void foo() {
319 *     Optional&lt;String&gt; i; // OK
320 *   }
321 *   public &lt;T extends java.util.Optional&gt; void method(T t) { // OK
322 *     Optional&lt;T&gt; i; // OK
323 *   }
324 * }
325 * </pre>
326 * <p>
327 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
328 * </p>
329 * <p>
330 * Violation Message Keys:
331 * </p>
332 * <ul>
333 * <li>
334 * {@code illegal.type}
335 * </li>
336 * </ul>
337 *
338 * @since 3.2
339 *
340 */
341@FileStatefulCheck
342public final class IllegalTypeCheck extends AbstractCheck {
343
344    /**
345     * A key is pointing to the warning message text in "messages.properties"
346     * file.
347     */
348    public static final String MSG_KEY = "illegal.type";
349
350    /** Types illegal by default. */
351    private static final String[] DEFAULT_ILLEGAL_TYPES = {
352        "HashSet",
353        "HashMap",
354        "LinkedHashMap",
355        "LinkedHashSet",
356        "TreeSet",
357        "TreeMap",
358        "java.util.HashSet",
359        "java.util.HashMap",
360        "java.util.LinkedHashMap",
361        "java.util.LinkedHashSet",
362        "java.util.TreeSet",
363        "java.util.TreeMap",
364    };
365
366    /** Default ignored method names. */
367    private static final String[] DEFAULT_IGNORED_METHOD_NAMES = {
368        "getInitialContext",
369        "getEnvironment",
370    };
371
372    /**
373     * Specify classes that should not be used as types in variable declarations,
374     * return values or parameters.
375     */
376    private final Set<String> illegalClassNames = new HashSet<>();
377    /** Illegal short classes. */
378    private final Set<String> illegalShortClassNames = new HashSet<>();
379    /** Define abstract classes that may be used as types. */
380    private final Set<String> legalAbstractClassNames = new HashSet<>();
381    /** Specify methods that should not be checked. */
382    private final Set<String> ignoredMethodNames = new HashSet<>();
383    /**
384     * Control whether to check only methods and fields with any of the specified modifiers.
385     * This property does not affect method calls nor method references nor record components.
386     */
387    @XdocsPropertyType(PropertyType.TOKEN_ARRAY)
388    private List<Integer> memberModifiers = Collections.emptyList();
389
390    /** Specify RegExp for illegal abstract class names. */
391    private Pattern illegalAbstractClassNameFormat = Pattern.compile("^(.*[.])?Abstract.*$");
392
393    /**
394     * Control whether to validate abstract class names.
395     */
396    private boolean validateAbstractClassNames;
397
398    /** Creates new instance of the check. */
399    public IllegalTypeCheck() {
400        setIllegalClassNames(DEFAULT_ILLEGAL_TYPES);
401        setIgnoredMethodNames(DEFAULT_IGNORED_METHOD_NAMES);
402    }
403
404    /**
405     * Setter to specify RegExp for illegal abstract class names.
406     *
407     * @param pattern a pattern.
408     */
409    public void setIllegalAbstractClassNameFormat(Pattern pattern) {
410        illegalAbstractClassNameFormat = pattern;
411    }
412
413    /**
414     * Setter to control whether to validate abstract class names.
415     *
416     * @param validateAbstractClassNames whether abstract class names must be ignored.
417     */
418    public void setValidateAbstractClassNames(boolean validateAbstractClassNames) {
419        this.validateAbstractClassNames = validateAbstractClassNames;
420    }
421
422    @Override
423    public int[] getDefaultTokens() {
424        return getAcceptableTokens();
425    }
426
427    @Override
428    public int[] getAcceptableTokens() {
429        return new int[] {
430            TokenTypes.ANNOTATION_FIELD_DEF,
431            TokenTypes.CLASS_DEF,
432            TokenTypes.IMPORT,
433            TokenTypes.INTERFACE_DEF,
434            TokenTypes.METHOD_CALL,
435            TokenTypes.METHOD_DEF,
436            TokenTypes.METHOD_REF,
437            TokenTypes.PARAMETER_DEF,
438            TokenTypes.VARIABLE_DEF,
439            TokenTypes.PATTERN_VARIABLE_DEF,
440            TokenTypes.RECORD_DEF,
441            TokenTypes.RECORD_COMPONENT_DEF,
442        };
443    }
444
445    @Override
446    public void beginTree(DetailAST rootAST) {
447        illegalShortClassNames.clear();
448        illegalShortClassNames.addAll(illegalClassNames);
449    }
450
451    @Override
452    public int[] getRequiredTokens() {
453        return new int[] {TokenTypes.IMPORT};
454    }
455
456    @Override
457    public void visitToken(DetailAST ast) {
458        switch (ast.getType()) {
459            case TokenTypes.CLASS_DEF:
460            case TokenTypes.INTERFACE_DEF:
461            case TokenTypes.RECORD_DEF:
462                visitTypeDef(ast);
463                break;
464            case TokenTypes.METHOD_CALL:
465            case TokenTypes.METHOD_REF:
466                visitMethodCallOrRef(ast);
467                break;
468            case TokenTypes.METHOD_DEF:
469                visitMethodDef(ast);
470                break;
471            case TokenTypes.VARIABLE_DEF:
472            case TokenTypes.ANNOTATION_FIELD_DEF:
473            case TokenTypes.PATTERN_VARIABLE_DEF:
474                visitVariableDef(ast);
475                break;
476            case TokenTypes.RECORD_COMPONENT_DEF:
477                checkClassName(ast);
478                break;
479            case TokenTypes.PARAMETER_DEF:
480                visitParameterDef(ast);
481                break;
482            case TokenTypes.IMPORT:
483                visitImport(ast);
484                break;
485            default:
486                throw new IllegalStateException(ast.toString());
487        }
488    }
489
490    /**
491     * Checks if current method's return type or variable's type is verifiable
492     * according to <b>memberModifiers</b> option.
493     *
494     * @param methodOrVariableDef METHOD_DEF or VARIABLE_DEF ast node.
495     * @return true if member is verifiable according to <b>memberModifiers</b> option.
496     */
497    private boolean isVerifiable(DetailAST methodOrVariableDef) {
498        boolean result = true;
499        if (!memberModifiers.isEmpty()) {
500            final DetailAST modifiersAst = methodOrVariableDef
501                    .findFirstToken(TokenTypes.MODIFIERS);
502            result = isContainVerifiableType(modifiersAst);
503        }
504        return result;
505    }
506
507    /**
508     * Checks is modifiers contain verifiable type.
509     *
510     * @param modifiers
511     *            parent node for all modifiers
512     * @return true if method or variable can be verified
513     */
514    private boolean isContainVerifiableType(DetailAST modifiers) {
515        boolean result = false;
516        for (DetailAST modifier = modifiers.getFirstChild(); modifier != null;
517                 modifier = modifier.getNextSibling()) {
518            if (memberModifiers.contains(modifier.getType())) {
519                result = true;
520                break;
521            }
522        }
523        return result;
524    }
525
526    /**
527     * Checks the super type and implemented interfaces of a given type.
528     *
529     * @param typeDef class or interface for check.
530     */
531    private void visitTypeDef(DetailAST typeDef) {
532        if (isVerifiable(typeDef)) {
533            checkTypeParameters(typeDef);
534            final DetailAST extendsClause = typeDef.findFirstToken(TokenTypes.EXTENDS_CLAUSE);
535            if (extendsClause != null) {
536                checkBaseTypes(extendsClause);
537            }
538            final DetailAST implementsClause = typeDef.findFirstToken(TokenTypes.IMPLEMENTS_CLAUSE);
539            if (implementsClause != null) {
540                checkBaseTypes(implementsClause);
541            }
542        }
543    }
544
545    /**
546     * Checks return type of a given method.
547     *
548     * @param methodDef method for check.
549     */
550    private void visitMethodDef(DetailAST methodDef) {
551        if (isCheckedMethod(methodDef)) {
552            checkClassName(methodDef);
553        }
554    }
555
556    /**
557     * Checks type of parameters.
558     *
559     * @param parameterDef parameter list for check.
560     */
561    private void visitParameterDef(DetailAST parameterDef) {
562        final DetailAST grandParentAST = parameterDef.getParent().getParent();
563
564        if (grandParentAST.getType() == TokenTypes.METHOD_DEF && isCheckedMethod(grandParentAST)) {
565            checkClassName(parameterDef);
566        }
567    }
568
569    /**
570     * Checks type of given variable.
571     *
572     * @param variableDef variable to check.
573     */
574    private void visitVariableDef(DetailAST variableDef) {
575        if (isVerifiable(variableDef)) {
576            checkClassName(variableDef);
577        }
578    }
579
580    /**
581     * Checks the type arguments of given method call/reference.
582     *
583     * @param methodCallOrRef method call/reference to check.
584     */
585    private void visitMethodCallOrRef(DetailAST methodCallOrRef) {
586        checkTypeArguments(methodCallOrRef);
587    }
588
589    /**
590     * Checks imported type (as static and star imports are not supported by Check,
591     *  only type is in the consideration).<br>
592     * If this type is illegal due to Check's options - puts violation on it.
593     *
594     * @param importAst {@link TokenTypes#IMPORT Import}
595     */
596    private void visitImport(DetailAST importAst) {
597        if (!isStarImport(importAst)) {
598            final String canonicalName = getImportedTypeCanonicalName(importAst);
599            extendIllegalClassNamesWithShortName(canonicalName);
600        }
601    }
602
603    /**
604     * Checks if current import is star import. E.g.:
605     * <p>
606     * {@code
607     * import java.util.*;
608     * }
609     * </p>
610     *
611     * @param importAst {@link TokenTypes#IMPORT Import}
612     * @return true if it is star import
613     */
614    private static boolean isStarImport(DetailAST importAst) {
615        boolean result = false;
616        DetailAST toVisit = importAst;
617        while (toVisit != null) {
618            toVisit = getNextSubTreeNode(toVisit, importAst);
619            if (toVisit != null && toVisit.getType() == TokenTypes.STAR) {
620                result = true;
621                break;
622            }
623        }
624        return result;
625    }
626
627    /**
628     * Checks type and type arguments/parameters of given method, parameter, variable or
629     * method call/reference.
630     *
631     * @param ast node to check.
632     */
633    private void checkClassName(DetailAST ast) {
634        final DetailAST type = ast.findFirstToken(TokenTypes.TYPE);
635        checkType(type);
636        checkTypeParameters(ast);
637    }
638
639    /**
640     * Checks the identifier of the given type.
641     *
642     * @param type node to check.
643     */
644    private void checkIdent(DetailAST type) {
645        final FullIdent ident = FullIdent.createFullIdent(type);
646        if (isMatchingClassName(ident.getText())) {
647            log(ident.getDetailAst(), MSG_KEY, ident.getText());
648        }
649    }
650
651    /**
652     * Checks the {@code extends} or {@code implements} statement.
653     *
654     * @param clause DetailAST for either {@link TokenTypes#EXTENDS_CLAUSE} or
655     *               {@link TokenTypes#IMPLEMENTS_CLAUSE}
656     */
657    private void checkBaseTypes(DetailAST clause) {
658        DetailAST child = clause.getFirstChild();
659        while (child != null) {
660            if (child.getType() == TokenTypes.IDENT) {
661                checkIdent(child);
662            }
663            else {
664                TokenUtil.forEachChild(child, TokenTypes.TYPE_ARGUMENT, this::checkType);
665            }
666            child = child.getNextSibling();
667        }
668    }
669
670    /**
671     * Checks the given type, its arguments and parameters.
672     *
673     * @param type node to check.
674     */
675    private void checkType(DetailAST type) {
676        checkIdent(type.getFirstChild());
677        checkTypeArguments(type);
678        checkTypeBounds(type);
679    }
680
681    /**
682     * Checks the upper and lower bounds for the given type.
683     *
684     * @param type node to check.
685     */
686    private void checkTypeBounds(DetailAST type) {
687        final DetailAST upperBounds = type.findFirstToken(TokenTypes.TYPE_UPPER_BOUNDS);
688        if (upperBounds != null) {
689            checkType(upperBounds);
690        }
691        final DetailAST lowerBounds = type.findFirstToken(TokenTypes.TYPE_LOWER_BOUNDS);
692        if (lowerBounds != null) {
693            checkType(lowerBounds);
694        }
695    }
696
697    /**
698     * Checks the type parameters of the node.
699     *
700     * @param node node to check.
701     */
702    private void checkTypeParameters(final DetailAST node) {
703        final DetailAST typeParameters = node.findFirstToken(TokenTypes.TYPE_PARAMETERS);
704        if (typeParameters != null) {
705            TokenUtil.forEachChild(typeParameters, TokenTypes.TYPE_PARAMETER, this::checkType);
706        }
707    }
708
709    /**
710     * Checks the type arguments of the node.
711     *
712     * @param node node to check.
713     */
714    private void checkTypeArguments(final DetailAST node) {
715        DetailAST typeArguments = node.findFirstToken(TokenTypes.TYPE_ARGUMENTS);
716        if (typeArguments == null) {
717            typeArguments = node.getFirstChild().findFirstToken(TokenTypes.TYPE_ARGUMENTS);
718        }
719
720        if (typeArguments != null) {
721            TokenUtil.forEachChild(typeArguments, TokenTypes.TYPE_ARGUMENT, this::checkType);
722        }
723    }
724
725    /**
726     * Returns true if given class name is one of illegal classes or else false.
727     *
728     * @param className class name to check.
729     * @return true if given class name is one of illegal classes
730     *         or if it matches to abstract class names pattern.
731     */
732    private boolean isMatchingClassName(String className) {
733        final String shortName = className.substring(className.lastIndexOf('.') + 1);
734        return illegalClassNames.contains(className)
735                || illegalShortClassNames.contains(shortName)
736                || validateAbstractClassNames
737                    && !legalAbstractClassNames.contains(className)
738                    && illegalAbstractClassNameFormat.matcher(className).find();
739    }
740
741    /**
742     * Extends illegal class names set via imported short type name.
743     *
744     * @param canonicalName
745     *     <a href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-6.html#jls-6.7">
746     *     Canonical</a> name of imported type.
747     */
748    private void extendIllegalClassNamesWithShortName(String canonicalName) {
749        if (illegalClassNames.contains(canonicalName)) {
750            final String shortName = canonicalName
751                .substring(canonicalName.lastIndexOf('.') + 1);
752            illegalShortClassNames.add(shortName);
753        }
754    }
755
756    /**
757     * Gets imported type's
758     * <a href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-6.html#jls-6.7">
759     *  canonical name</a>.
760     *
761     * @param importAst {@link TokenTypes#IMPORT Import}
762     * @return Imported canonical type's name.
763     */
764    private static String getImportedTypeCanonicalName(DetailAST importAst) {
765        final StringBuilder canonicalNameBuilder = new StringBuilder(256);
766        DetailAST toVisit = importAst;
767        while (toVisit != null) {
768            toVisit = getNextSubTreeNode(toVisit, importAst);
769            if (toVisit != null && toVisit.getType() == TokenTypes.IDENT) {
770                if (canonicalNameBuilder.length() > 0) {
771                    canonicalNameBuilder.append('.');
772                }
773                canonicalNameBuilder.append(toVisit.getText());
774            }
775        }
776        return canonicalNameBuilder.toString();
777    }
778
779    /**
780     * Gets the next node of a syntactical tree (child of a current node or
781     * sibling of a current node, or sibling of a parent of a current node).
782     *
783     * @param currentNodeAst Current node in considering
784     * @param subTreeRootAst SubTree root
785     * @return Current node after bypassing, if current node reached the root of a subtree
786     *        method returns null
787     */
788    private static DetailAST
789        getNextSubTreeNode(DetailAST currentNodeAst, DetailAST subTreeRootAst) {
790        DetailAST currentNode = currentNodeAst;
791        DetailAST toVisitAst = currentNode.getFirstChild();
792        while (toVisitAst == null) {
793            toVisitAst = currentNode.getNextSibling();
794            if (currentNode.getParent().equals(subTreeRootAst)) {
795                break;
796            }
797            currentNode = currentNode.getParent();
798        }
799        return toVisitAst;
800    }
801
802    /**
803     * Returns true if method has to be checked or false.
804     *
805     * @param ast method def to check.
806     * @return true if we should check this method.
807     */
808    private boolean isCheckedMethod(DetailAST ast) {
809        final String methodName =
810            ast.findFirstToken(TokenTypes.IDENT).getText();
811        return isVerifiable(ast) && !ignoredMethodNames.contains(methodName)
812                && !AnnotationUtil.containsAnnotation(ast, "Override");
813    }
814
815    /**
816     * Setter to specify classes that should not be used as types in variable declarations,
817     * return values or parameters.
818     *
819     * @param classNames array of illegal variable types
820     * @noinspection WeakerAccess
821     */
822    public void setIllegalClassNames(String... classNames) {
823        illegalClassNames.clear();
824        Collections.addAll(illegalClassNames, classNames);
825    }
826
827    /**
828     * Setter to specify methods that should not be checked.
829     *
830     * @param methodNames array of ignored method names
831     * @noinspection WeakerAccess
832     */
833    public void setIgnoredMethodNames(String... methodNames) {
834        ignoredMethodNames.clear();
835        Collections.addAll(ignoredMethodNames, methodNames);
836    }
837
838    /**
839     * Setter to define abstract classes that may be used as types.
840     *
841     * @param classNames array of legal abstract class names
842     * @noinspection WeakerAccess
843     */
844    public void setLegalAbstractClassNames(String... classNames) {
845        Collections.addAll(legalAbstractClassNames, classNames);
846    }
847
848    /**
849     * Setter to control whether to check only methods and fields with any of
850     * the specified modifiers.
851     * This property does not affect method calls nor method references nor record components.
852     *
853     * @param modifiers String contains modifiers.
854     */
855    public void setMemberModifiers(String modifiers) {
856        memberModifiers = Stream.of(modifiers.split(","))
857            .map(String::trim)
858            .filter(token -> !token.isEmpty())
859            .map(TokenUtil::getTokenId)
860            .collect(Collectors.toList());
861    }
862
863}