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.javadoc;
21
22 import java.util.Locale;
23
24 import com.puppycrawl.tools.checkstyle.StatelessCheck;
25 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
26 import com.puppycrawl.tools.checkstyle.api.DetailAST;
27 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
28 import com.puppycrawl.tools.checkstyle.utils.JavadocUtil;
29 import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
30
31 /**
32 * <div>
33 * Checks that the Javadoc content begins from the same position
34 * for all Javadoc comments in the project. Any leading asterisks and spaces
35 * are not counted as the beginning of the content and are therefore ignored.
36 * </div>
37 *
38 * <p>
39 * It is possible to enforce two different styles:
40 * </p>
41 * <ul>
42 * <li>
43 * {@code first_line} - Javadoc content starts from the first line:
44 * <div class="wrapper"><pre class="prettyprint"><code class="language-java">
45 * /** Summary text.
46 * * More details.
47 * */
48 * public void method();
49 * </code></pre></div>
50 * </li>
51 * <li>
52 * {@code second_line} - Javadoc content starts from the second line:
53 * <div class="wrapper"><pre class="prettyprint"><code class="language-java">
54 * /**
55 * * Summary text.
56 * * More details.
57 * */
58 * public void method();
59 * </code></pre></div>
60 * </li>
61 * </ul>
62 *
63 * <p>
64 * Notes:
65 * This check does not validate the Javadoc summary itself nor its presence.
66 * The check will not report any violations for missing or malformed javadoc summary.
67 * To validate the Javadoc summary use
68 * <a href="https://checkstyle.org/checks/javadoc/summaryjavadoc.html">
69 * SummaryJavadoc</a> check.
70 * </p>
71 *
72 * <p>
73 * The <a href="https://docs.oracle.com/en/java/javase/17/docs/specs/javadoc/doc-comment-spec.html">
74 * Documentation Comment Specification</a> permits leading asterisks on the first line.
75 * For these Javadoc comments:
76 * </p>
77 * <div class="wrapper"><pre class="prettyprint"><code class="language-java">
78 * /***
79 * * Some text.
80 * */
81 * /************
82 * * Some text.
83 * */
84 * /** **
85 * * Some text.
86 * */
87 * </code></pre></div>
88 *
89 * <p>
90 * The documentation generated will be just "Some text." without any asterisks.
91 * Since these asterisks will not appear in the generated documentation,
92 * they should not be considered as the beginning of the Javadoc content.
93 * In such cases, the check assumes that the Javadoc content begins on the second line.
94 * </p>
95 *
96 * @since 8.27
97 */
98 @StatelessCheck
99 public class JavadocContentLocationCheck extends AbstractCheck {
100
101 /**
102 * A key is pointing to the warning message text in "messages.properties" file.
103 */
104 public static final String MSG_JAVADOC_CONTENT_FIRST_LINE = "javadoc.content.first.line";
105
106 /**
107 * A key is pointing to the warning message text in "messages.properties" file.
108 */
109 public static final String MSG_JAVADOC_CONTENT_SECOND_LINE = "javadoc.content.second.line";
110
111 /**
112 * Specify the policy on placement of the Javadoc content.
113 */
114 private JavadocContentLocationOption location = JavadocContentLocationOption.SECOND_LINE;
115
116 @Override
117 public int[] getRequiredTokens() {
118 return new int[] {
119 TokenTypes.BLOCK_COMMENT_BEGIN,
120 };
121 }
122
123 @Override
124 public int[] getAcceptableTokens() {
125 return getRequiredTokens();
126 }
127
128 @Override
129 public int[] getDefaultTokens() {
130 return getRequiredTokens();
131 }
132
133 @Override
134 public boolean isCommentNodesRequired() {
135 return true;
136 }
137
138 /**
139 * Setter to specify the policy on placement of the Javadoc content.
140 *
141 * @param value string to decode location from
142 * @throws IllegalArgumentException if unable to decode
143 * @since 8.27
144 */
145 public void setLocation(String value) {
146 location = JavadocContentLocationOption.valueOf(value.trim().toUpperCase(Locale.ENGLISH));
147 }
148
149 @Override
150 public void visitToken(DetailAST ast) {
151 if (isMultilineComment(ast) && JavadocUtil.isJavadocComment(ast)) {
152 final String commentContent = JavadocUtil.getJavadocCommentContent(ast);
153 final int indexOfFirstNonBlankLine = findIndexOfFirstNonBlankLine(commentContent);
154 if (indexOfFirstNonBlankLine >= 0) {
155 if (location == JavadocContentLocationOption.FIRST_LINE
156 && indexOfFirstNonBlankLine != 0) {
157 log(ast, MSG_JAVADOC_CONTENT_FIRST_LINE);
158 }
159 else if (location == JavadocContentLocationOption.SECOND_LINE
160 && indexOfFirstNonBlankLine != 1) {
161 log(ast, MSG_JAVADOC_CONTENT_SECOND_LINE);
162 }
163 }
164 }
165 }
166
167 /**
168 * Checks if a DetailAST of type {@code TokenTypes.BLOCK_COMMENT_BEGIN} span
169 * more than one line. The node always has at least one child of the type
170 * {@code TokenTypes.BLOCK_COMMENT_END}.
171 *
172 * @param node node to check
173 * @return {@code true} for multi-line comment nodes
174 */
175 private static boolean isMultilineComment(DetailAST node) {
176 return !TokenUtil.areOnSameLine(node, node.getLastChild());
177 }
178
179 /**
180 * Returns the index of the first non-blank line.
181 * All lines consists only of asterisks and whitespaces are treated as blank.
182 *
183 * @param commentContent Javadoc content to process
184 * @return the index of the first non-blank line or {@code -1} if all lines are blank
185 */
186 private static int findIndexOfFirstNonBlankLine(String commentContent) {
187 int lineNo = 0;
188 boolean noContent = true;
189 for (int i = 0; i < commentContent.length(); ++i) {
190 final char character = commentContent.charAt(i);
191 if (character == '\n') {
192 ++lineNo;
193 }
194 else if (character != '*' && !Character.isWhitespace(character)) {
195 noContent = false;
196 break;
197 }
198 }
199 if (noContent) {
200 lineNo = -1;
201 }
202 return lineNo;
203 }
204
205 }