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RedundantImportCheck.java
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RedundantImportCheck.java
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////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2020 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.checks.imports;
import java.util.HashSet;
import java.util.Set;
import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.FullIdent;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
/**
* <p>
* Checks for redundant import statements. An import statement is
* considered redundant if:
* </p>
* <ul>
* <li>It is a duplicate of another import. This is, when a class is imported
* more than once.</li>
* <li>The class non-statically imported is from the {@code java.lang}
* package, e.g. importing {@code java.lang.String}.</li>
* <li>The class non-statically imported is from the same package as the
* current package.</li>
* </ul>
* <p>
* To configure the check:
* </p>
* <pre>
* <module name="RedundantImport"/>
* </pre>
*
* @since 3.0
*/
@FileStatefulCheck
public class RedundantImportCheck
extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_LANG = "import.lang";
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_SAME = "import.same";
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_DUPLICATE = "import.duplicate";
/** Set of the imports. */
private final Set<FullIdent> imports = new HashSet<>();
/** Set of static imports. */
private final Set<FullIdent> staticImports = new HashSet<>();
/** Name of package in file. */
private String pkgName;
@Override
public void beginTree(DetailAST aRootAST) {
pkgName = null;
imports.clear();
staticImports.clear();
}
@Override
public int[] getDefaultTokens() {
return getRequiredTokens();
}
@Override
public int[] getAcceptableTokens() {
return getRequiredTokens();
}
@Override
public int[] getRequiredTokens() {
return new int[] {
TokenTypes.IMPORT, TokenTypes.STATIC_IMPORT, TokenTypes.PACKAGE_DEF,
};
}
@Override
public void visitToken(DetailAST ast) {
if (ast.getType() == TokenTypes.PACKAGE_DEF) {
pkgName = FullIdent.createFullIdent(
ast.getLastChild().getPreviousSibling()).getText();
}
else if (ast.getType() == TokenTypes.IMPORT) {
final FullIdent imp = FullIdent.createFullIdentBelow(ast);
if (isFromPackage(imp.getText(), "java.lang")) {
log(ast, MSG_LANG, imp.getText());
}
// imports from unnamed package are not allowed,
// so we are checking SAME rule only for named packages
else if (pkgName != null && isFromPackage(imp.getText(), pkgName)) {
log(ast, MSG_SAME, imp.getText());
}
// Check for a duplicate import
imports.stream().filter(full -> imp.getText().equals(full.getText()))
.forEach(full -> log(ast, MSG_DUPLICATE, full.getLineNo(), imp.getText()));
imports.add(imp);
}
else {
// Check for a duplicate static import
final FullIdent imp =
FullIdent.createFullIdent(
ast.getLastChild().getPreviousSibling());
staticImports.stream().filter(full -> imp.getText().equals(full.getText()))
.forEach(full -> log(ast, MSG_DUPLICATE, full.getLineNo(), imp.getText()));
staticImports.add(imp);
}
}
/**
* Determines if an import statement is for types from a specified package.
* @param importName the import name
* @param pkg the package name
* @return whether from the package
*/
private static boolean isFromPackage(String importName, String pkg) {
// imports from unnamed package are not allowed:
// https://docs.oracle.com/javase/specs/jls/se7/html/jls-7.html#jls-7.5
// So '.' must be present in member name and we are not checking for it
final int index = importName.lastIndexOf('.');
final String front = importName.substring(0, index);
return pkg.equals(front);
}
}