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1   ///////////////////////////////////////////////////////////////////////////////////////////////
2   // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3   // Copyright (C) 2001-2025 the original author or authors.
4   //
5   // This library is free software; you can redistribute it and/or
6   // modify it under the terms of the GNU Lesser General Public
7   // License as published by the Free Software Foundation; either
8   // version 2.1 of the License, or (at your option) any later version.
9   //
10  // This library is distributed in the hope that it will be useful,
11  // but WITHOUT ANY WARRANTY; without even the implied warranty of
12  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13  // Lesser General Public License for more details.
14  //
15  // You should have received a copy of the GNU Lesser General Public
16  // License along with this library; if not, write to the Free Software
17  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18  ///////////////////////////////////////////////////////////////////////////////////////////////
19  
20  package com.puppycrawl.tools.checkstyle.checks.design;
21  
22  import java.util.ArrayList;
23  import java.util.Collection;
24  import java.util.HashSet;
25  import java.util.List;
26  import java.util.Set;
27  import java.util.regex.Pattern;
28  import java.util.stream.Collectors;
29  
30  import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
31  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
32  import com.puppycrawl.tools.checkstyle.api.DetailAST;
33  import com.puppycrawl.tools.checkstyle.api.FullIdent;
34  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
35  import com.puppycrawl.tools.checkstyle.utils.AnnotationUtil;
36  import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
37  import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
38  
39  /**
40   * <div>
41   * Checks visibility of class members. Only static final, immutable or annotated
42   * by specified annotation members may be public;
43   * other class members must be private unless the property {@code protectedAllowed}
44   * or {@code packageAllowed} is set.
45   * </div>
46   *
47   * <p>
48   * Public members are not flagged if the name matches the public
49   * member regular expression (contains {@code "^serialVersionUID$"} by
50   * default).
51   * </p>
52   *
53   * <p>
54   * Note that Checkstyle 2 used to include {@code "^f[A-Z][a-zA-Z0-9]*$"} in the default pattern
55   * to allow names used in container-managed persistence for Enterprise JavaBeans (EJB) 1.1 with
56   * the default settings. With EJB 2.0 it is no longer necessary to have public access for
57   * persistent fields, so the default has been changed.
58   * </p>
59   *
60   * <p>
61   * Rationale: Enforce encapsulation.
62   * </p>
63   *
64   * <p>
65   * Check also has options making it less strict:
66   * </p>
67   *
68   * <p>
69   * <b>ignoreAnnotationCanonicalNames</b> - the list of annotations which ignore
70   * variables in consideration. If user want to provide short annotation name that
71   * type will match to any named the same type without consideration of package.
72   * </p>
73   *
74   * <p>
75   * <b>allowPublicFinalFields</b> - which allows public final fields.
76   * </p>
77   *
78   * <p>
79   * <b>allowPublicImmutableFields</b> - which allows immutable fields to be
80   * declared as public if defined in final class.
81   * </p>
82   *
83   * <p>
84   * Field is known to be immutable if:
85   * </p>
86   * <ul>
87   * <li>It's declared as final</li>
88   * <li>Has either a primitive type or instance of class user defined to be immutable
89   * (such as String, ImmutableCollection from Guava, etc.)</li>
90   * </ul>
91   *
92   * <p>
93   * Classes known to be immutable are listed in <b>immutableClassCanonicalNames</b>
94   * by their canonical names.
95   * </p>
96   *
97   * <p>
98   * Property Rationale: Forcing all fields of class to have private modifier by default is
99   * good in most cases, but in some cases it drawbacks in too much boilerplate get/set code.
100  * One of such cases are immutable classes.
101  * </p>
102  *
103  * <p>
104  * Restriction: Check doesn't check if class is immutable, there's no checking
105  * if accessory methods are missing and all fields are immutable, we only check
106  * if current field is immutable or final.
107  * Under the flag <b>allowPublicImmutableFields</b>, the enclosing class must
108  * also be final, to encourage immutability.
109  * Under the flag <b>allowPublicFinalFields</b>, the final modifier
110  * on the enclosing class is optional.
111  * </p>
112  *
113  * <p>
114  * Star imports are out of scope of this Check. So if one of type imported via
115  * star import collides with user specified one by its short name - there
116  * won't be Check's violation.
117  * </p>
118  * <ul>
119  * <li>
120  * Property {@code allowPublicFinalFields} - Allow final fields to be declared as public.
121  * Type is {@code boolean}.
122  * Default value is {@code false}.
123  * </li>
124  * <li>
125  * Property {@code allowPublicImmutableFields} - Allow immutable fields to be
126  * declared as public if defined in final class.
127  * Type is {@code boolean}.
128  * Default value is {@code false}.
129  * </li>
130  * <li>
131  * Property {@code ignoreAnnotationCanonicalNames} - Specify annotations canonical
132  * names which ignore variables in consideration.
133  * Type is {@code java.lang.String[]}.
134  * Default value is {@code com.google.common.annotations.VisibleForTesting,
135  * org.junit.ClassRule, org.junit.Rule}.
136  * </li>
137  * <li>
138  * Property {@code immutableClassCanonicalNames} - Specify immutable classes canonical names.
139  * Type is {@code java.lang.String[]}.
140  * Default value is {@code java.io.File, java.lang.Boolean, java.lang.Byte,
141  * java.lang.Character, java.lang.Double, java.lang.Float, java.lang.Integer,
142  * java.lang.Long, java.lang.Short, java.lang.StackTraceElement, java.lang.String,
143  * java.math.BigDecimal, java.math.BigInteger, java.net.Inet4Address, java.net.Inet6Address,
144  * java.net.InetSocketAddress, java.net.URI, java.net.URL, java.util.Locale, java.util.UUID}.
145  * </li>
146  * <li>
147  * Property {@code packageAllowed} - Control whether package visible members are allowed.
148  * Type is {@code boolean}.
149  * Default value is {@code false}.
150  * </li>
151  * <li>
152  * Property {@code protectedAllowed} - Control whether protected members are allowed.
153  * Type is {@code boolean}.
154  * Default value is {@code false}.
155  * </li>
156  * <li>
157  * Property {@code publicMemberPattern} - Specify pattern for public members that should be ignored.
158  * Type is {@code java.util.regex.Pattern}.
159  * Default value is {@code "^serialVersionUID$"}.
160  * </li>
161  * </ul>
162  *
163  * <p>
164  * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
165  * </p>
166  *
167  * <p>
168  * Violation Message Keys:
169  * </p>
170  * <ul>
171  * <li>
172  * {@code variable.notPrivate}
173  * </li>
174  * </ul>
175  *
176  * @since 3.0
177  */
178 @FileStatefulCheck
179 public class VisibilityModifierCheck
180     extends AbstractCheck {
181 
182     /**
183      * A key is pointing to the warning message text in "messages.properties"
184      * file.
185      */
186     public static final String MSG_KEY = "variable.notPrivate";
187 
188     /** Default immutable types canonical names. */
189     private static final Set<String> DEFAULT_IMMUTABLE_TYPES = Set.of(
190         "java.lang.String",
191         "java.lang.Integer",
192         "java.lang.Byte",
193         "java.lang.Character",
194         "java.lang.Short",
195         "java.lang.Boolean",
196         "java.lang.Long",
197         "java.lang.Double",
198         "java.lang.Float",
199         "java.lang.StackTraceElement",
200         "java.math.BigInteger",
201         "java.math.BigDecimal",
202         "java.io.File",
203         "java.util.Locale",
204         "java.util.UUID",
205         "java.net.URL",
206         "java.net.URI",
207         "java.net.Inet4Address",
208         "java.net.Inet6Address",
209         "java.net.InetSocketAddress"
210     );
211 
212     /** Default ignore annotations canonical names. */
213     private static final Set<String> DEFAULT_IGNORE_ANNOTATIONS = Set.of(
214         "org.junit.Rule",
215         "org.junit.ClassRule",
216         "com.google.common.annotations.VisibleForTesting"
217     );
218 
219     /** Name for 'public' access modifier. */
220     private static final String PUBLIC_ACCESS_MODIFIER = "public";
221 
222     /** Name for 'private' access modifier. */
223     private static final String PRIVATE_ACCESS_MODIFIER = "private";
224 
225     /** Name for 'protected' access modifier. */
226     private static final String PROTECTED_ACCESS_MODIFIER = "protected";
227 
228     /** Name for implicit 'package' access modifier. */
229     private static final String PACKAGE_ACCESS_MODIFIER = "package";
230 
231     /** Name for 'static' keyword. */
232     private static final String STATIC_KEYWORD = "static";
233 
234     /** Name for 'final' keyword. */
235     private static final String FINAL_KEYWORD = "final";
236 
237     /** Contains explicit access modifiers. */
238     private static final String[] EXPLICIT_MODS = {
239         PUBLIC_ACCESS_MODIFIER,
240         PRIVATE_ACCESS_MODIFIER,
241         PROTECTED_ACCESS_MODIFIER,
242     };
243 
244     /**
245      * Specify pattern for public members that should be ignored.
246      */
247     private Pattern publicMemberPattern = Pattern.compile("^serialVersionUID$");
248 
249     /** Set of ignore annotations short names. */
250     private Set<String> ignoreAnnotationShortNames;
251 
252     /** Set of immutable classes short names. */
253     private Set<String> immutableClassShortNames;
254 
255     /**
256      * Specify annotations canonical names which ignore variables in
257      * consideration.
258      */
259     private Set<String> ignoreAnnotationCanonicalNames = DEFAULT_IGNORE_ANNOTATIONS;
260 
261     /** Control whether protected members are allowed. */
262     private boolean protectedAllowed;
263 
264     /** Control whether package visible members are allowed. */
265     private boolean packageAllowed;
266 
267     /** Allow immutable fields to be declared as public if defined in final class. */
268     private boolean allowPublicImmutableFields;
269 
270     /** Allow final fields to be declared as public. */
271     private boolean allowPublicFinalFields;
272 
273     /** Specify immutable classes canonical names. */
274     private Set<String> immutableClassCanonicalNames = DEFAULT_IMMUTABLE_TYPES;
275 
276     /**
277      * Setter to specify annotations canonical names which ignore variables
278      * in consideration.
279      *
280      * @param annotationNames array of ignore annotations canonical names.
281      * @since 6.5
282      */
283     public void setIgnoreAnnotationCanonicalNames(String... annotationNames) {
284         ignoreAnnotationCanonicalNames = Set.of(annotationNames);
285     }
286 
287     /**
288      * Setter to control whether protected members are allowed.
289      *
290      * @param protectedAllowed whether protected members are allowed
291      * @since 3.0
292      */
293     public void setProtectedAllowed(boolean protectedAllowed) {
294         this.protectedAllowed = protectedAllowed;
295     }
296 
297     /**
298      * Setter to control whether package visible members are allowed.
299      *
300      * @param packageAllowed whether package visible members are allowed
301      * @since 3.0
302      */
303     public void setPackageAllowed(boolean packageAllowed) {
304         this.packageAllowed = packageAllowed;
305     }
306 
307     /**
308      * Setter to specify pattern for public members that should be ignored.
309      *
310      * @param pattern
311      *        pattern for public members to ignore.
312      * @since 3.0
313      */
314     public void setPublicMemberPattern(Pattern pattern) {
315         publicMemberPattern = pattern;
316     }
317 
318     /**
319      * Setter to allow immutable fields to be declared as public if defined in final class.
320      *
321      * @param allow user's value.
322      * @since 6.4
323      */
324     public void setAllowPublicImmutableFields(boolean allow) {
325         allowPublicImmutableFields = allow;
326     }
327 
328     /**
329      * Setter to allow final fields to be declared as public.
330      *
331      * @param allow user's value.
332      * @since 7.0
333      */
334     public void setAllowPublicFinalFields(boolean allow) {
335         allowPublicFinalFields = allow;
336     }
337 
338     /**
339      * Setter to specify immutable classes canonical names.
340      *
341      * @param classNames array of immutable types canonical names.
342      * @since 6.4.1
343      */
344     public void setImmutableClassCanonicalNames(String... classNames) {
345         immutableClassCanonicalNames = Set.of(classNames);
346     }
347 
348     @Override
349     public int[] getDefaultTokens() {
350         return getRequiredTokens();
351     }
352 
353     @Override
354     public int[] getAcceptableTokens() {
355         return getRequiredTokens();
356     }
357 
358     @Override
359     public int[] getRequiredTokens() {
360         return new int[] {
361             TokenTypes.VARIABLE_DEF,
362             TokenTypes.IMPORT,
363         };
364     }
365 
366     @Override
367     public void beginTree(DetailAST rootAst) {
368         immutableClassShortNames = getClassShortNames(immutableClassCanonicalNames);
369         ignoreAnnotationShortNames = getClassShortNames(ignoreAnnotationCanonicalNames);
370     }
371 
372     @Override
373     public void visitToken(DetailAST ast) {
374         switch (ast.getType()) {
375             case TokenTypes.VARIABLE_DEF -> {
376                 if (!isAnonymousClassVariable(ast)) {
377                     visitVariableDef(ast);
378                 }
379             }
380             case TokenTypes.IMPORT -> visitImport(ast);
381             default -> {
382                 final String exceptionMsg = "Unexpected token type: " + ast.getText();
383                 throw new IllegalArgumentException(exceptionMsg);
384             }
385         }
386     }
387 
388     /**
389      * Checks if current variable definition is definition of an anonymous class.
390      *
391      * @param variableDef {@link TokenTypes#VARIABLE_DEF VARIABLE_DEF}
392      * @return true if current variable definition is definition of an anonymous class.
393      */
394     private static boolean isAnonymousClassVariable(DetailAST variableDef) {
395         return variableDef.getParent().getType() != TokenTypes.OBJBLOCK;
396     }
397 
398     /**
399      * Checks access modifier of given variable.
400      * If it is not proper according to Check - puts violation on it.
401      *
402      * @param variableDef variable to check.
403      */
404     private void visitVariableDef(DetailAST variableDef) {
405         final boolean inInterfaceOrAnnotationBlock =
406                 ScopeUtil.isInInterfaceOrAnnotationBlock(variableDef);
407 
408         if (!inInterfaceOrAnnotationBlock && !hasIgnoreAnnotation(variableDef)) {
409             final DetailAST varNameAST = variableDef.findFirstToken(TokenTypes.TYPE)
410                 .getNextSibling();
411             final String varName = varNameAST.getText();
412             if (!hasProperAccessModifier(variableDef, varName)) {
413                 log(varNameAST, MSG_KEY, varName);
414             }
415         }
416     }
417 
418     /**
419      * Checks if variable def has ignore annotation.
420      *
421      * @param variableDef {@link TokenTypes#VARIABLE_DEF VARIABLE_DEF}
422      * @return true if variable def has ignore annotation.
423      */
424     private boolean hasIgnoreAnnotation(DetailAST variableDef) {
425         final DetailAST firstIgnoreAnnotation =
426                  findMatchingAnnotation(variableDef);
427         return firstIgnoreAnnotation != null;
428     }
429 
430     /**
431      * Checks imported type. If type's canonical name was not specified in
432      * <b>immutableClassCanonicalNames</b>, but its short name collides with one from
433      * <b>immutableClassShortNames</b> - removes it from the last one.
434      *
435      * @param importAst {@link TokenTypes#IMPORT Import}
436      */
437     private void visitImport(DetailAST importAst) {
438         if (!isStarImport(importAst)) {
439             final String canonicalName = getCanonicalName(importAst);
440             final String shortName = getClassShortName(canonicalName);
441 
442             // If imported canonical class name is not specified as allowed immutable class,
443             // but its short name collides with one of specified class - removes the short name
444             // from list to avoid names collision
445             if (!immutableClassCanonicalNames.contains(canonicalName)) {
446                 immutableClassShortNames.remove(shortName);
447             }
448             if (!ignoreAnnotationCanonicalNames.contains(canonicalName)) {
449                 ignoreAnnotationShortNames.remove(shortName);
450             }
451         }
452     }
453 
454     /**
455      * Checks if current import is star import. E.g.:
456      *
457      * <p>
458      * {@code
459      * import java.util.*;
460      * }
461      * </p>
462      *
463      * @param importAst {@link TokenTypes#IMPORT Import}
464      * @return true if it is star import
465      */
466     private static boolean isStarImport(DetailAST importAst) {
467         boolean result = false;
468         DetailAST toVisit = importAst;
469         while (toVisit != null) {
470             toVisit = getNextSubTreeNode(toVisit, importAst);
471             if (toVisit != null && toVisit.getType() == TokenTypes.STAR) {
472                 result = true;
473                 break;
474             }
475         }
476         return result;
477     }
478 
479     /**
480      * Checks if current variable has proper access modifier according to Check's options.
481      *
482      * @param variableDef Variable definition node.
483      * @param variableName Variable's name.
484      * @return true if variable has proper access modifier.
485      */
486     private boolean hasProperAccessModifier(DetailAST variableDef, String variableName) {
487         boolean result = true;
488 
489         final String variableScope = getVisibilityScope(variableDef);
490 
491         if (!PRIVATE_ACCESS_MODIFIER.equals(variableScope)) {
492             result =
493                 isStaticFinalVariable(variableDef)
494                 || packageAllowed && PACKAGE_ACCESS_MODIFIER.equals(variableScope)
495                 || protectedAllowed && PROTECTED_ACCESS_MODIFIER.equals(variableScope)
496                 || isIgnoredPublicMember(variableName, variableScope)
497                 || isAllowedPublicField(variableDef);
498         }
499 
500         return result;
501     }
502 
503     /**
504      * Checks whether variable has static final modifiers.
505      *
506      * @param variableDef Variable definition node.
507      * @return true of variable has static final modifiers.
508      */
509     private static boolean isStaticFinalVariable(DetailAST variableDef) {
510         final Set<String> modifiers = getModifiers(variableDef);
511         return modifiers.contains(STATIC_KEYWORD)
512                 && modifiers.contains(FINAL_KEYWORD);
513     }
514 
515     /**
516      * Checks whether variable belongs to public members that should be ignored.
517      *
518      * @param variableName Variable's name.
519      * @param variableScope Variable's scope.
520      * @return true if variable belongs to public members that should be ignored.
521      */
522     private boolean isIgnoredPublicMember(String variableName, String variableScope) {
523         return PUBLIC_ACCESS_MODIFIER.equals(variableScope)
524             && publicMemberPattern.matcher(variableName).find();
525     }
526 
527     /**
528      * Checks whether the variable satisfies the public field check.
529      *
530      * @param variableDef Variable definition node.
531      * @return true if allowed.
532      */
533     private boolean isAllowedPublicField(DetailAST variableDef) {
534         return allowPublicFinalFields && isFinalField(variableDef)
535             || allowPublicImmutableFields && isImmutableFieldDefinedInFinalClass(variableDef);
536     }
537 
538     /**
539      * Checks whether immutable field is defined in final class.
540      *
541      * @param variableDef Variable definition node.
542      * @return true if immutable field is defined in final class.
543      */
544     private boolean isImmutableFieldDefinedInFinalClass(DetailAST variableDef) {
545         final DetailAST classDef = variableDef.getParent().getParent();
546         final Set<String> classModifiers = getModifiers(classDef);
547         return (classModifiers.contains(FINAL_KEYWORD) || classDef.getType() == TokenTypes.ENUM_DEF)
548                 && isImmutableField(variableDef);
549     }
550 
551     /**
552      * Returns the set of modifier Strings for a VARIABLE_DEF or CLASS_DEF AST.
553      *
554      * @param defAST AST for a variable or class definition.
555      * @return the set of modifier Strings for defAST.
556      */
557     private static Set<String> getModifiers(DetailAST defAST) {
558         final DetailAST modifiersAST = defAST.findFirstToken(TokenTypes.MODIFIERS);
559         final Set<String> modifiersSet = new HashSet<>();
560         if (modifiersAST != null) {
561             DetailAST modifier = modifiersAST.getFirstChild();
562             while (modifier != null) {
563                 modifiersSet.add(modifier.getText());
564                 modifier = modifier.getNextSibling();
565             }
566         }
567         return modifiersSet;
568     }
569 
570     /**
571      * Returns the visibility scope for the variable.
572      *
573      * @param variableDef Variable definition node.
574      * @return one of "public", "private", "protected", "package"
575      */
576     private static String getVisibilityScope(DetailAST variableDef) {
577         final Set<String> modifiers = getModifiers(variableDef);
578         String accessModifier = PACKAGE_ACCESS_MODIFIER;
579         for (final String modifier : EXPLICIT_MODS) {
580             if (modifiers.contains(modifier)) {
581                 accessModifier = modifier;
582                 break;
583             }
584         }
585         return accessModifier;
586     }
587 
588     /**
589      * Checks if current field is immutable:
590      * has final modifier and either a primitive type or instance of class
591      * known to be immutable (such as String, ImmutableCollection from Guava, etc.).
592      * Classes known to be immutable are listed in
593      * {@link VisibilityModifierCheck#immutableClassCanonicalNames}
594      *
595      * @param variableDef Field in consideration.
596      * @return true if field is immutable.
597      */
598     private boolean isImmutableField(DetailAST variableDef) {
599         boolean result = false;
600         if (isFinalField(variableDef)) {
601             final DetailAST type = variableDef.findFirstToken(TokenTypes.TYPE);
602             final boolean isCanonicalName = isCanonicalName(type);
603             final String typeName = getCanonicalName(type);
604             if (immutableClassShortNames.contains(typeName)
605                     || isCanonicalName && immutableClassCanonicalNames.contains(typeName)) {
606                 final DetailAST typeArgs = getGenericTypeArgs(type, isCanonicalName);
607 
608                 if (typeArgs == null) {
609                     result = true;
610                 }
611                 else {
612                     final List<String> argsClassNames = getTypeArgsClassNames(typeArgs);
613                     result = areImmutableTypeArguments(argsClassNames);
614                 }
615             }
616             else {
617                 result = !isCanonicalName && isPrimitive(type);
618             }
619         }
620         return result;
621     }
622 
623     /**
624      * Checks whether type definition is in canonical form.
625      *
626      * @param type type definition token.
627      * @return true if type definition is in canonical form.
628      */
629     private static boolean isCanonicalName(DetailAST type) {
630         return type.getFirstChild().getType() == TokenTypes.DOT;
631     }
632 
633     /**
634      * Returns generic type arguments token.
635      *
636      * @param type type token.
637      * @param isCanonicalName whether type name is in canonical form.
638      * @return generic type arguments token.
639      */
640     private static DetailAST getGenericTypeArgs(DetailAST type, boolean isCanonicalName) {
641         final DetailAST typeArgs;
642         if (isCanonicalName) {
643             // if type class name is in canonical form, abstract tree has specific structure
644             typeArgs = type.getFirstChild().findFirstToken(TokenTypes.TYPE_ARGUMENTS);
645         }
646         else {
647             typeArgs = type.findFirstToken(TokenTypes.TYPE_ARGUMENTS);
648         }
649         return typeArgs;
650     }
651 
652     /**
653      * Returns a list of type parameters class names.
654      *
655      * @param typeArgs type arguments token.
656      * @return a list of type parameters class names.
657      */
658     private static List<String> getTypeArgsClassNames(DetailAST typeArgs) {
659         final List<String> typeClassNames = new ArrayList<>();
660         DetailAST type = typeArgs.findFirstToken(TokenTypes.TYPE_ARGUMENT);
661         DetailAST sibling;
662         do {
663             final String typeName = getCanonicalName(type);
664             typeClassNames.add(typeName);
665             sibling = type.getNextSibling();
666             type = sibling.getNextSibling();
667         } while (sibling.getType() == TokenTypes.COMMA);
668         return typeClassNames;
669     }
670 
671     /**
672      * Checks whether all generic type arguments are immutable.
673      * If at least one argument is mutable, we assume that the whole list of type arguments
674      * is mutable.
675      *
676      * @param typeArgsClassNames type arguments class names.
677      * @return true if all generic type arguments are immutable.
678      */
679     private boolean areImmutableTypeArguments(Collection<String> typeArgsClassNames) {
680         return typeArgsClassNames.stream().noneMatch(
681             typeName -> {
682                 return !immutableClassShortNames.contains(typeName)
683                     && !immutableClassCanonicalNames.contains(typeName);
684             });
685     }
686 
687     /**
688      * Checks whether current field is final.
689      *
690      * @param variableDef field in consideration.
691      * @return true if current field is final.
692      */
693     private static boolean isFinalField(DetailAST variableDef) {
694         final DetailAST modifiers = variableDef.findFirstToken(TokenTypes.MODIFIERS);
695         return modifiers.findFirstToken(TokenTypes.FINAL) != null;
696     }
697 
698     /**
699      * Checks if current type is primitive type (int, short, float, boolean, double, etc.).
700      * As primitive types have special tokens for each one, such as:
701      * LITERAL_INT, LITERAL_BOOLEAN, etc.
702      * So, if type's identifier differs from {@link TokenTypes#IDENT IDENT} token - it's a
703      * primitive type.
704      *
705      * @param type Ast {@link TokenTypes#TYPE TYPE} node.
706      * @return true if current type is primitive type.
707      */
708     private static boolean isPrimitive(DetailAST type) {
709         return type.getFirstChild().getType() != TokenTypes.IDENT;
710     }
711 
712     /**
713      * Gets canonical type's name from given {@link TokenTypes#TYPE TYPE} node.
714      *
715      * @param type DetailAST {@link TokenTypes#TYPE TYPE} node.
716      * @return canonical type's name
717      */
718     private static String getCanonicalName(DetailAST type) {
719         final StringBuilder canonicalNameBuilder = new StringBuilder(256);
720         DetailAST toVisit = type;
721         while (toVisit != null) {
722             toVisit = getNextSubTreeNode(toVisit, type);
723             if (toVisit != null && toVisit.getType() == TokenTypes.IDENT) {
724                 if (!canonicalNameBuilder.isEmpty()) {
725                     canonicalNameBuilder.append('.');
726                 }
727                 canonicalNameBuilder.append(toVisit.getText());
728                 final DetailAST nextSubTreeNode = getNextSubTreeNode(toVisit, type);
729                 if (nextSubTreeNode != null
730                         && nextSubTreeNode.getType() == TokenTypes.TYPE_ARGUMENTS) {
731                     break;
732                 }
733             }
734         }
735         return canonicalNameBuilder.toString();
736     }
737 
738     /**
739      * Gets the next node of a syntactical tree (child of a current node or
740      * sibling of a current node, or sibling of a parent of a current node).
741      *
742      * @param currentNodeAst Current node in considering
743      * @param subTreeRootAst SubTree root
744      * @return Current node after bypassing, if current node reached the root of a subtree
745      *        method returns null
746      */
747     private static DetailAST
748         getNextSubTreeNode(DetailAST currentNodeAst, DetailAST subTreeRootAst) {
749         DetailAST currentNode = currentNodeAst;
750         DetailAST toVisitAst = currentNode.getFirstChild();
751         while (toVisitAst == null) {
752             toVisitAst = currentNode.getNextSibling();
753             if (currentNode.getParent().getColumnNo() == subTreeRootAst.getColumnNo()) {
754                 break;
755             }
756             currentNode = currentNode.getParent();
757         }
758         return toVisitAst;
759     }
760 
761     /**
762      * Converts canonical class names to short names.
763      *
764      * @param canonicalClassNames the set of canonical class names.
765      * @return the set of short names of classes.
766      */
767     private static Set<String> getClassShortNames(Set<String> canonicalClassNames) {
768         return canonicalClassNames.stream()
769             .map(CommonUtil::baseClassName)
770             .collect(Collectors.toCollection(HashSet::new));
771     }
772 
773     /**
774      * Gets the short class name from given canonical name.
775      *
776      * @param canonicalClassName canonical class name.
777      * @return short name of class.
778      */
779     private static String getClassShortName(String canonicalClassName) {
780         return canonicalClassName
781                 .substring(canonicalClassName.lastIndexOf('.') + 1);
782     }
783 
784     /**
785      * Checks whether the AST is annotated with
786      * an annotation containing the passed in regular
787      * expression and return the AST representing that
788      * annotation.
789      *
790      * <p>
791      * This method will not look for imports or package
792      * statements to detect the passed in annotation.
793      * </p>
794      *
795      * <p>
796      * To check if an AST contains a passed in annotation
797      * taking into account fully-qualified names
798      * (ex: java.lang.Override, Override)
799      * this method will need to be called twice. Once for each
800      * name given.
801      * </p>
802      *
803      * @param variableDef {@link TokenTypes#VARIABLE_DEF variable def node}.
804      * @return the AST representing the first such annotation or null if
805      *         no such annotation was found
806      */
807     private DetailAST findMatchingAnnotation(DetailAST variableDef) {
808         DetailAST matchingAnnotation = null;
809 
810         final DetailAST holder = AnnotationUtil.getAnnotationHolder(variableDef);
811 
812         for (DetailAST child = holder.getFirstChild();
813             child != null; child = child.getNextSibling()) {
814             if (child.getType() == TokenTypes.ANNOTATION) {
815                 final DetailAST ast = child.getFirstChild();
816                 final String name =
817                     FullIdent.createFullIdent(ast.getNextSibling()).getText();
818                 if (ignoreAnnotationCanonicalNames.contains(name)
819                          || ignoreAnnotationShortNames.contains(name)) {
820                     matchingAnnotation = child;
821                     break;
822                 }
823             }
824         }
825 
826         return matchingAnnotation;
827     }
828 
829 }