001//////////////////////////////////////////////////////////////////////////////// 002// checkstyle: Checks Java source code for adherence to a set of rules. 003// Copyright (C) 2001-2015 the original author or authors. 004// 005// This library is free software; you can redistribute it and/or 006// modify it under the terms of the GNU Lesser General Public 007// License as published by the Free Software Foundation; either 008// version 2.1 of the License, or (at your option) any later version. 009// 010// This library is distributed in the hope that it will be useful, 011// but WITHOUT ANY WARRANTY; without even the implied warranty of 012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 013// Lesser General Public License for more details. 014// 015// You should have received a copy of the GNU Lesser General Public 016// License along with this library; if not, write to the Free Software 017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 018//////////////////////////////////////////////////////////////////////////////// 019 020package com.puppycrawl.tools.checkstyle.checks.imports; 021 022import java.util.Set; 023 024import com.google.common.collect.Sets; 025import com.puppycrawl.tools.checkstyle.api.Check; 026import com.puppycrawl.tools.checkstyle.api.DetailAST; 027import com.puppycrawl.tools.checkstyle.api.FullIdent; 028import com.puppycrawl.tools.checkstyle.api.TokenTypes; 029 030/** 031 * <p> 032 * Checks for imports that are redundant. An import statement is 033 * considered redundant if: 034 * </p> 035 *<ul> 036 * <li>It is a duplicate of another import. This is, when a class is imported 037 * more than once.</li> 038 * <li>The class non-statically imported is from the {@code java.lang} 039 * package. For example importing {@code java.lang.String}.</li> 040 * <li>The class non-statically imported is from the same package as the 041 * current package.</li> 042 *</ul> 043 * <p> 044 * An example of how to configure the check is: 045 * </p> 046 * <pre> 047 * <module name="RedundantImport"/> 048 * </pre> 049 * Compatible with Java 1.5 source. 050 * 051 * @author Oliver Burn 052 */ 053public class RedundantImportCheck 054 extends Check { 055 056 /** 057 * A key is pointing to the warning message text in "messages.properties" 058 * file. 059 */ 060 public static final String MSG_LANG = "import.lang"; 061 062 /** 063 * A key is pointing to the warning message text in "messages.properties" 064 * file. 065 */ 066 public static final String MSG_SAME = "import.same"; 067 068 /** 069 * A key is pointing to the warning message text in "messages.properties" 070 * file. 071 */ 072 public static final String MSG_DUPLICATE = "import.duplicate"; 073 074 /** Name of package in file. */ 075 private String pkgName; 076 /** Set of the imports. */ 077 private final Set<FullIdent> imports = Sets.newHashSet(); 078 /** Set of static imports. */ 079 private final Set<FullIdent> staticImports = Sets.newHashSet(); 080 081 @Override 082 public void beginTree(DetailAST aRootAST) { 083 pkgName = null; 084 imports.clear(); 085 staticImports.clear(); 086 } 087 088 @Override 089 public int[] getDefaultTokens() { 090 return getAcceptableTokens(); 091 } 092 093 @Override 094 public int[] getAcceptableTokens() { 095 return new int[] 096 {TokenTypes.IMPORT, 097 TokenTypes.STATIC_IMPORT, 098 TokenTypes.PACKAGE_DEF, }; 099 } 100 101 @Override 102 public int[] getRequiredTokens() { 103 return getAcceptableTokens(); 104 } 105 106 @Override 107 public void visitToken(DetailAST ast) { 108 if (ast.getType() == TokenTypes.PACKAGE_DEF) { 109 pkgName = FullIdent.createFullIdent( 110 ast.getLastChild().getPreviousSibling()).getText(); 111 } 112 else if (ast.getType() == TokenTypes.IMPORT) { 113 final FullIdent imp = FullIdent.createFullIdentBelow(ast); 114 if (isFromPackage(imp.getText(), "java.lang")) { 115 log(ast.getLineNo(), ast.getColumnNo(), MSG_LANG, 116 imp.getText()); 117 } 118 // imports from unnamed package are not allowed, 119 // so we are checking SAME rule only for named packages 120 else if (pkgName != null && isFromPackage(imp.getText(), pkgName)) { 121 log(ast.getLineNo(), ast.getColumnNo(), MSG_SAME, 122 imp.getText()); 123 } 124 // Check for a duplicate import 125 for (FullIdent full : imports) { 126 if (imp.getText().equals(full.getText())) { 127 log(ast.getLineNo(), ast.getColumnNo(), 128 MSG_DUPLICATE, full.getLineNo(), 129 imp.getText()); 130 } 131 } 132 133 imports.add(imp); 134 } 135 else { 136 // Check for a duplicate static import 137 final FullIdent imp = 138 FullIdent.createFullIdent( 139 ast.getLastChild().getPreviousSibling()); 140 for (FullIdent full : staticImports) { 141 if (imp.getText().equals(full.getText())) { 142 log(ast.getLineNo(), ast.getColumnNo(), 143 MSG_DUPLICATE, full.getLineNo(), imp.getText()); 144 } 145 } 146 147 staticImports.add(imp); 148 } 149 } 150 151 /** 152 * Determines if an import statement is for types from a specified package. 153 * @param importName the import name 154 * @param pkg the package name 155 * @return whether from the package 156 */ 157 private static boolean isFromPackage(String importName, String pkg) { 158 // imports from unnamed package are not allowed: 159 // http://docs.oracle.com/javase/specs/jls/se7/html/jls-7.html#jls-7.5 160 // So '.' must be present in member name and we are not checking for it 161 final int index = importName.lastIndexOf('.'); 162 final String front = importName.substring(0, index); 163 return front.equals(pkg); 164 } 165}