1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2026 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.imports;
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.FullIdent;
26 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
27 import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
28
29 /**
30 * <div>
31 * Checks that there are no static import statements.
32 * </div>
33 *
34 * <p>
35 * Rationale: Importing static members can lead to naming conflicts
36 * between class' members. It may lead to poor code readability since it
37 * may no longer be clear what class a member resides in (without looking
38 * at the import statement).
39 * </p>
40 *
41 * <p>
42 * Notes:
43 * If you exclude a starred import on a class this automatically excludes
44 * each member individually.
45 * </p>
46 *
47 * <p>
48 * For example: Excluding {@code java.lang.Math.*}. will allow the import
49 * of each static member in the Math class individually like
50 * {@code java.lang.Math.PI, java.lang.Math.cos, ...}.
51 * </p>
52 *
53 * @since 5.0
54 */
55 @StatelessCheck
56 public class AvoidStaticImportCheck
57 extends AbstractCheck {
58
59 /**
60 * A key is pointing to the warning message text in "messages.properties"
61 * file.
62 */
63 public static final String MSG_KEY = "import.avoidStatic";
64
65 /**
66 * Control whether to allow for certain classes via a star notation to be
67 * excluded such as {@code java.lang.Math.*} or specific static members
68 * to be excluded like {@code java.lang.System.out} for a variable or
69 * {@code java.lang.Math.random} for a method. See notes section for details.
70 */
71 private String[] excludes = CommonUtil.EMPTY_STRING_ARRAY;
72
73 /**
74 * Creates a new {@code AvoidStaticImportCheck} instance.
75 */
76 public AvoidStaticImportCheck() {
77 // no code by default
78 }
79
80 @Override
81 public int[] getDefaultTokens() {
82 return getRequiredTokens();
83 }
84
85 @Override
86 public int[] getAcceptableTokens() {
87 return getRequiredTokens();
88 }
89
90 @Override
91 public int[] getRequiredTokens() {
92 return new int[] {TokenTypes.STATIC_IMPORT};
93 }
94
95 /**
96 * Setter to control whether to allow for certain classes via a star notation
97 * to be excluded such as {@code java.lang.Math.*} or specific static members
98 * to be excluded like {@code java.lang.System.out} for a variable or
99 * {@code java.lang.Math.random} for a method. See notes section for details.
100 *
101 * @param excludes fully-qualified class names/specific
102 * static members where static imports are ok
103 * @since 5.0
104 */
105 public void setExcludes(String... excludes) {
106 this.excludes = excludes.clone();
107 }
108
109 @Override
110 public void visitToken(final DetailAST ast) {
111 final DetailAST startingDot =
112 ast.getFirstChild().getNextSibling();
113 final FullIdent name = FullIdent.createFullIdent(startingDot);
114
115 final String nameText = name.getText();
116 if (!isExempt(nameText)) {
117 log(startingDot, MSG_KEY, nameText);
118 }
119 }
120
121 /**
122 * Checks if a class or static member is exempt from known excludes.
123 *
124 * @param classOrStaticMember
125 * the class or static member
126 * @return true if except false if not
127 */
128 private boolean isExempt(String classOrStaticMember) {
129 boolean exempt = false;
130
131 for (String exclude : excludes) {
132 if (classOrStaticMember.equals(exclude)
133 || isStarImportOfPackage(classOrStaticMember, exclude)) {
134 exempt = true;
135 break;
136 }
137 }
138 return exempt;
139 }
140
141 /**
142 * Returns true if classOrStaticMember is a starred name of package,
143 * not just member name.
144 *
145 * @param classOrStaticMember - full name of member
146 * @param exclude - current exclusion
147 * @return true if member in exclusion list
148 */
149 private static boolean isStarImportOfPackage(String classOrStaticMember, String exclude) {
150 boolean result = false;
151 if (exclude.endsWith(".*")) {
152 // this section allows explicit imports
153 // to be exempt when configured using
154 // a starred import
155 final String excludeMinusDotStar =
156 exclude.substring(0, exclude.length() - 2);
157 if (classOrStaticMember.startsWith(excludeMinusDotStar)
158 && !classOrStaticMember.equals(excludeMinusDotStar)) {
159 final String member = classOrStaticMember.substring(
160 excludeMinusDotStar.length() + 1);
161 // if it contains a dot then it is not a member but a package
162 if (member.indexOf('.') == -1) {
163 result = true;
164 }
165 }
166 }
167 return result;
168 }
169
170 }