1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2024 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.modifier;
21
22 import com.puppycrawl.tools.checkstyle.StatelessCheck;
23 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
24 import com.puppycrawl.tools.checkstyle.api.DetailAST;
25 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
26 import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
27
28 /**
29 * <div>
30 * Checks for implicit modifiers on interface members and nested types.
31 * </div>
32 *
33 * <p>
34 * This check is effectively the opposite of
35 * <a href="https://checkstyle.org/checks/modifier/redundantmodifier.html#RedundantModifier">
36 * RedundantModifier</a>.
37 * It checks the modifiers on interface members, ensuring that certain modifiers are explicitly
38 * specified even though they are actually redundant.
39 * </p>
40 *
41 * <p>
42 * Methods in interfaces are {@code public} by default, however from Java 9 they can also be
43 * {@code private}. This check provides the ability to enforce that {@code public} is explicitly
44 * coded and not implicitly added by the compiler.
45 * </p>
46 *
47 * <p>
48 * From Java 8, there are three types of methods in interfaces - static methods marked with
49 * {@code static}, default methods marked with {@code default} and abstract methods which do not
50 * have to be marked with anything. From Java 9, there are also private methods marked with
51 * {@code private}. This check provides the ability to enforce that {@code abstract} is
52 * explicitly coded and not implicitly added by the compiler.
53 * </p>
54 *
55 * <p>
56 * Fields in interfaces are always {@code public static final} and as such the compiler does not
57 * require these modifiers. This check provides the ability to enforce that these modifiers are
58 * explicitly coded and not implicitly added by the compiler.
59 * </p>
60 *
61 * <p>
62 * Nested types within an interface are always {@code public static} and as such the compiler
63 * does not require the {@code public static} modifiers. This check provides the ability to
64 * enforce that the {@code public} and {@code static} modifiers are explicitly coded and not
65 * implicitly added by the compiler.
66 * </p>
67 * <pre>
68 * public interface AddressFactory {
69 * // check enforces code contains "public static final"
70 * public static final String UNKNOWN = "Unknown";
71 *
72 * String OTHER = "Other"; // violation
73 *
74 * // check enforces code contains "public" or "private"
75 * public static AddressFactory instance();
76 *
77 * // check enforces code contains "public abstract"
78 * public abstract Address createAddress(String addressLine, String city);
79 *
80 * List<Address> findAddresses(String city); // violation
81 *
82 * // check enforces default methods are explicitly declared "public"
83 * public default Address createAddress(String city) {
84 * return createAddress(UNKNOWN, city);
85 * }
86 *
87 * default Address createOtherAddress() { // violation
88 * return createAddress(OTHER, OTHER);
89 * }
90 * }
91 * </pre>
92 *
93 * <p>
94 * Rationale for this check: Methods, fields and nested types are treated differently
95 * depending on whether they are part of an interface or part of a class. For example, by
96 * default methods are package-scoped on classes, but public in interfaces. However, from
97 * Java 8 onwards, interfaces have changed to be much more like abstract classes.
98 * Interfaces now have static and instance methods with code. Developers should not have to
99 * remember which modifiers are required and which are implied. This check allows the simpler
100 * alternative approach to be adopted where the implied modifiers must always be coded explicitly.
101 * </p>
102 * <ul>
103 * <li>
104 * Property {@code violateImpliedAbstractMethod} - Control whether to enforce that {@code abstract}
105 * is explicitly coded on interface methods.
106 * Type is {@code boolean}.
107 * Default value is {@code true}.
108 * </li>
109 * <li>
110 * Property {@code violateImpliedFinalField} - Control whether to enforce that {@code final}
111 * is explicitly coded on interface fields.
112 * Type is {@code boolean}.
113 * Default value is {@code true}.
114 * </li>
115 * <li>
116 * Property {@code violateImpliedPublicField} - Control whether to enforce that {@code public}
117 * is explicitly coded on interface fields.
118 * Type is {@code boolean}.
119 * Default value is {@code true}.
120 * </li>
121 * <li>
122 * Property {@code violateImpliedPublicMethod} - Control whether to enforce that {@code public}
123 * is explicitly coded on interface methods.
124 * Type is {@code boolean}.
125 * Default value is {@code true}.
126 * </li>
127 * <li>
128 * Property {@code violateImpliedPublicNested} - Control whether to enforce that {@code public}
129 * is explicitly coded on interface nested types.
130 * Type is {@code boolean}.
131 * Default value is {@code true}.
132 * </li>
133 * <li>
134 * Property {@code violateImpliedStaticField} - Control whether to enforce that {@code static}
135 * is explicitly coded on interface fields.
136 * Type is {@code boolean}.
137 * Default value is {@code true}.
138 * </li>
139 * <li>
140 * Property {@code violateImpliedStaticNested} - Control whether to enforce that {@code static}
141 * is explicitly coded on interface nested types.
142 * Type is {@code boolean}.
143 * Default value is {@code true}.
144 * </li>
145 * </ul>
146 *
147 * <p>
148 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
149 * </p>
150 *
151 * <p>
152 * Violation Message Keys:
153 * </p>
154 * <ul>
155 * <li>
156 * {@code interface.implied.modifier}
157 * </li>
158 * </ul>
159 *
160 * @since 8.12
161 */
162 @StatelessCheck
163 public class InterfaceMemberImpliedModifierCheck
164 extends AbstractCheck {
165
166 /**
167 * A key is pointing to the warning message text in "messages.properties" file.
168 */
169 public static final String MSG_KEY = "interface.implied.modifier";
170
171 /** Name for 'public' access modifier. */
172 private static final String PUBLIC_ACCESS_MODIFIER = "public";
173
174 /** Name for 'abstract' keyword. */
175 private static final String ABSTRACT_KEYWORD = "abstract";
176
177 /** Name for 'static' keyword. */
178 private static final String STATIC_KEYWORD = "static";
179
180 /** Name for 'final' keyword. */
181 private static final String FINAL_KEYWORD = "final";
182
183 /**
184 * Control whether to enforce that {@code public} is explicitly coded
185 * on interface fields.
186 */
187 private boolean violateImpliedPublicField = true;
188
189 /**
190 * Control whether to enforce that {@code static} is explicitly coded
191 * on interface fields.
192 */
193 private boolean violateImpliedStaticField = true;
194
195 /**
196 * Control whether to enforce that {@code final} is explicitly coded
197 * on interface fields.
198 */
199 private boolean violateImpliedFinalField = true;
200
201 /**
202 * Control whether to enforce that {@code public} is explicitly coded
203 * on interface methods.
204 */
205 private boolean violateImpliedPublicMethod = true;
206
207 /**
208 * Control whether to enforce that {@code abstract} is explicitly coded
209 * on interface methods.
210 */
211 private boolean violateImpliedAbstractMethod = true;
212
213 /**
214 * Control whether to enforce that {@code public} is explicitly coded
215 * on interface nested types.
216 */
217 private boolean violateImpliedPublicNested = true;
218
219 /**
220 * Control whether to enforce that {@code static} is explicitly coded
221 * on interface nested types.
222 */
223 private boolean violateImpliedStaticNested = true;
224
225 /**
226 * Setter to control whether to enforce that {@code public} is explicitly coded
227 * on interface fields.
228 *
229 * @param violateImpliedPublicField
230 * True to perform the check, false to turn the check off.
231 * @since 8.12
232 */
233 public void setViolateImpliedPublicField(boolean violateImpliedPublicField) {
234 this.violateImpliedPublicField = violateImpliedPublicField;
235 }
236
237 /**
238 * Setter to control whether to enforce that {@code static} is explicitly coded
239 * on interface fields.
240 *
241 * @param violateImpliedStaticField
242 * True to perform the check, false to turn the check off.
243 * @since 8.12
244 */
245 public void setViolateImpliedStaticField(boolean violateImpliedStaticField) {
246 this.violateImpliedStaticField = violateImpliedStaticField;
247 }
248
249 /**
250 * Setter to control whether to enforce that {@code final} is explicitly coded
251 * on interface fields.
252 *
253 * @param violateImpliedFinalField
254 * True to perform the check, false to turn the check off.
255 * @since 8.12
256 */
257 public void setViolateImpliedFinalField(boolean violateImpliedFinalField) {
258 this.violateImpliedFinalField = violateImpliedFinalField;
259 }
260
261 /**
262 * Setter to control whether to enforce that {@code public} is explicitly coded
263 * on interface methods.
264 *
265 * @param violateImpliedPublicMethod
266 * True to perform the check, false to turn the check off.
267 * @since 8.12
268 */
269 public void setViolateImpliedPublicMethod(boolean violateImpliedPublicMethod) {
270 this.violateImpliedPublicMethod = violateImpliedPublicMethod;
271 }
272
273 /**
274 * Setter to control whether to enforce that {@code abstract} is explicitly coded
275 * on interface methods.
276 *
277 * @param violateImpliedAbstractMethod
278 * True to perform the check, false to turn the check off.
279 * @since 8.12
280 */
281 public void setViolateImpliedAbstractMethod(boolean violateImpliedAbstractMethod) {
282 this.violateImpliedAbstractMethod = violateImpliedAbstractMethod;
283 }
284
285 /**
286 * Setter to control whether to enforce that {@code public} is explicitly coded
287 * on interface nested types.
288 *
289 * @param violateImpliedPublicNested
290 * True to perform the check, false to turn the check off.
291 * @since 8.12
292 */
293 public void setViolateImpliedPublicNested(boolean violateImpliedPublicNested) {
294 this.violateImpliedPublicNested = violateImpliedPublicNested;
295 }
296
297 /**
298 * Setter to control whether to enforce that {@code static} is explicitly coded
299 * on interface nested types.
300 *
301 * @param violateImpliedStaticNested
302 * True to perform the check, false to turn the check off.
303 * @since 8.12
304 */
305 public void setViolateImpliedStaticNested(boolean violateImpliedStaticNested) {
306 this.violateImpliedStaticNested = violateImpliedStaticNested;
307 }
308
309 @Override
310 public int[] getDefaultTokens() {
311 return getAcceptableTokens();
312 }
313
314 @Override
315 public int[] getRequiredTokens() {
316 return getAcceptableTokens();
317 }
318
319 @Override
320 public int[] getAcceptableTokens() {
321 return new int[] {
322 TokenTypes.METHOD_DEF,
323 TokenTypes.VARIABLE_DEF,
324 TokenTypes.INTERFACE_DEF,
325 TokenTypes.CLASS_DEF,
326 TokenTypes.ENUM_DEF,
327 };
328 }
329
330 @Override
331 public void visitToken(DetailAST ast) {
332 if (ScopeUtil.isInInterfaceBlock(ast) && !ScopeUtil.isInCodeBlock(ast)) {
333 switch (ast.getType()) {
334 case TokenTypes.METHOD_DEF:
335 processMethod(ast);
336 break;
337 case TokenTypes.VARIABLE_DEF:
338 processField(ast);
339 break;
340 case TokenTypes.CLASS_DEF:
341 case TokenTypes.INTERFACE_DEF:
342 case TokenTypes.ENUM_DEF:
343 processNestedType(ast);
344 break;
345 default:
346 throw new IllegalStateException(ast.toString());
347 }
348 }
349 }
350
351 /**
352 * Check method in interface.
353 *
354 * @param ast the method AST
355 */
356 private void processMethod(DetailAST ast) {
357 final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
358 if (violateImpliedPublicMethod
359 && modifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) == null
360 && modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
361 log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
362 }
363 if (violateImpliedAbstractMethod
364 && modifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) == null
365 && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null
366 && modifiers.findFirstToken(TokenTypes.LITERAL_DEFAULT) == null
367 && modifiers.findFirstToken(TokenTypes.ABSTRACT) == null) {
368 log(ast, MSG_KEY, ABSTRACT_KEYWORD);
369 }
370 }
371
372 /**
373 * Check field in interface.
374 *
375 * @param ast the field AST
376 */
377 private void processField(DetailAST ast) {
378 final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
379 if (violateImpliedPublicField
380 && modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
381 log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
382 }
383 if (violateImpliedStaticField
384 && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
385 log(ast, MSG_KEY, STATIC_KEYWORD);
386 }
387 if (violateImpliedFinalField
388 && modifiers.findFirstToken(TokenTypes.FINAL) == null) {
389 log(ast, MSG_KEY, FINAL_KEYWORD);
390 }
391 }
392
393 /**
394 * Check nested types in interface.
395 *
396 * @param ast the nested type AST
397 */
398 private void processNestedType(DetailAST ast) {
399 final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
400 if (violateImpliedPublicNested
401 && modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
402 log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
403 }
404 if (violateImpliedStaticNested
405 && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
406 log(ast, MSG_KEY, STATIC_KEYWORD);
407 }
408 }
409
410 }