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