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.imports;
21
22 import java.util.HashSet;
23 import java.util.Set;
24
25 import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
26 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
27 import com.puppycrawl.tools.checkstyle.api.DetailAST;
28 import com.puppycrawl.tools.checkstyle.api.FullIdent;
29 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
30
31 /**
32 * <div>
33 * Checks for redundant import statements. An import statement is
34 * considered redundant if:
35 * </div>
36 * <ul>
37 * <li>It is a duplicate of another import. This is, when a class is imported
38 * more than once.</li>
39 * <li>The class non-statically imported is from the {@code java.lang}
40 * package, e.g. importing {@code java.lang.String}.</li>
41 * <li>The class non-statically imported is from the same package as the
42 * current package.</li>
43 * </ul>
44 *
45 * <p>
46 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
47 * </p>
48 *
49 * <p>
50 * Violation Message Keys:
51 * </p>
52 * <ul>
53 * <li>
54 * {@code import.duplicate}
55 * </li>
56 * <li>
57 * {@code import.lang}
58 * </li>
59 * <li>
60 * {@code import.same}
61 * </li>
62 * </ul>
63 *
64 * @since 3.0
65 */
66 @FileStatefulCheck
67 public class RedundantImportCheck
68 extends AbstractCheck {
69
70 /**
71 * A key is pointing to the warning message text in "messages.properties"
72 * file.
73 */
74 public static final String MSG_LANG = "import.lang";
75
76 /**
77 * A key is pointing to the warning message text in "messages.properties"
78 * file.
79 */
80 public static final String MSG_SAME = "import.same";
81
82 /**
83 * A key is pointing to the warning message text in "messages.properties"
84 * file.
85 */
86 public static final String MSG_DUPLICATE = "import.duplicate";
87
88 /** Set of the imports. */
89 private final Set<FullIdent> imports = new HashSet<>();
90 /** Set of static imports. */
91 private final Set<FullIdent> staticImports = new HashSet<>();
92
93 /** Name of package in file. */
94 private String pkgName;
95
96 @Override
97 public void beginTree(DetailAST aRootAST) {
98 pkgName = null;
99 imports.clear();
100 staticImports.clear();
101 }
102
103 @Override
104 public int[] getDefaultTokens() {
105 return getRequiredTokens();
106 }
107
108 @Override
109 public int[] getAcceptableTokens() {
110 return getRequiredTokens();
111 }
112
113 @Override
114 public int[] getRequiredTokens() {
115 return new int[] {
116 TokenTypes.IMPORT, TokenTypes.STATIC_IMPORT, TokenTypes.PACKAGE_DEF,
117 };
118 }
119
120 @Override
121 public void visitToken(DetailAST ast) {
122 if (ast.getType() == TokenTypes.PACKAGE_DEF) {
123 pkgName = FullIdent.createFullIdent(
124 ast.getLastChild().getPreviousSibling()).getText();
125 }
126 else if (ast.getType() == TokenTypes.IMPORT) {
127 final FullIdent imp = FullIdent.createFullIdentBelow(ast);
128 final String importText = imp.getText();
129 if (isFromPackage(importText, "java.lang")) {
130 log(ast, MSG_LANG, importText);
131 }
132 // imports from unnamed package are not allowed,
133 // so we are checking SAME rule only for named packages
134 else if (pkgName != null && isFromPackage(importText, pkgName)) {
135 log(ast, MSG_SAME, importText);
136 }
137 // Check for a duplicate import
138 imports.stream().filter(full -> importText.equals(full.getText()))
139 .forEach(full -> log(ast, MSG_DUPLICATE, full.getLineNo(), importText));
140
141 imports.add(imp);
142 }
143 else {
144 // Check for a duplicate static import
145 final FullIdent imp =
146 FullIdent.createFullIdent(
147 ast.getLastChild().getPreviousSibling());
148 staticImports.stream().filter(full -> imp.getText().equals(full.getText()))
149 .forEach(full -> log(ast, MSG_DUPLICATE, full.getLineNo(), imp.getText()));
150
151 staticImports.add(imp);
152 }
153 }
154
155 /**
156 * Determines if an import statement is for types from a specified package.
157 *
158 * @param importName the import name
159 * @param pkg the package name
160 * @return whether from the package
161 */
162 private static boolean isFromPackage(String importName, String pkg) {
163 // imports from unnamed package are not allowed:
164 // https://docs.oracle.com/javase/specs/jls/se7/html/jls-7.html#jls-7.5
165 // So '.' must be present in member name and we are not checking for it
166 final int index = importName.lastIndexOf('.');
167 final String front = importName.substring(0, index);
168 return pkg.equals(front);
169 }
170
171 }