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Checkstyle is a development tool to help programmers write Java code
that adheres to a coding standard
///////////////////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
// Copyright (C) 2001-2024 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;
import java.util.Optional;
import java.util.Set;
import java.util.regex.Pattern;
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;
/**
*
* Detects uncommented {@code main} methods.
*
*
*
* Rationale: A {@code main} method is often used for debugging purposes.
* When debugging is finished, developers often forget to remove the method,
* which changes the API and increases the size of the resulting class or JAR file.
* Except for the real program entry points, all {@code main} methods
* should be removed or commented out of the sources.
*
*
* -
* Property {@code excludedClasses} - Specify pattern for qualified names of
* classes which are allowed to have a {@code main} method.
* Type is {@code java.util.regex.Pattern}.
* Default value is {@code "^$"}.
*
*
*
*
* Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
*
*
*
* Violation Message Keys:
*
*
* -
* {@code uncommented.main}
*
*
*
* @since 3.2
*/
@FileStatefulCheck
public class UncommentedMainCheck
extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "uncommented.main";
/** Set of possible String array types. */
private static final Set STRING_PARAMETER_NAMES = Set.of(
String[].class.getCanonicalName(),
String.class.getCanonicalName(),
String[].class.getSimpleName(),
String.class.getSimpleName()
);
/**
* Specify pattern for qualified names of classes which are allowed to
* have a {@code main} method.
*/
private Pattern excludedClasses = Pattern.compile("^$");
/** Current class name. */
private String currentClass;
/** Current package. */
private FullIdent packageName;
/** Class definition depth. */
private int classDepth;
/**
* Setter to specify pattern for qualified names of classes which are allowed
* to have a {@code main} method.
*
* @param excludedClasses a pattern
* @since 3.2
*/
public void setExcludedClasses(Pattern excludedClasses) {
this.excludedClasses = excludedClasses;
}
@Override
public int[] getAcceptableTokens() {
return getRequiredTokens();
}
@Override
public int[] getDefaultTokens() {
return getRequiredTokens();
}
@Override
public int[] getRequiredTokens() {
return new int[] {
TokenTypes.METHOD_DEF,
TokenTypes.CLASS_DEF,
TokenTypes.PACKAGE_DEF,
TokenTypes.RECORD_DEF,
};
}
@Override
public void beginTree(DetailAST rootAST) {
packageName = FullIdent.createFullIdent(null);
classDepth = 0;
}
@Override
public void leaveToken(DetailAST ast) {
if (ast.getType() == TokenTypes.CLASS_DEF) {
classDepth--;
}
}
@Override
public void visitToken(DetailAST ast) {
switch (ast.getType()) {
case TokenTypes.PACKAGE_DEF:
visitPackageDef(ast);
break;
case TokenTypes.RECORD_DEF:
case TokenTypes.CLASS_DEF:
visitClassOrRecordDef(ast);
break;
case TokenTypes.METHOD_DEF:
visitMethodDef(ast);
break;
default:
throw new IllegalStateException(ast.toString());
}
}
/**
* Sets current package.
*
* @param packageDef node for package definition
*/
private void visitPackageDef(DetailAST packageDef) {
packageName = FullIdent.createFullIdent(packageDef.getLastChild()
.getPreviousSibling());
}
/**
* If not inner class then change current class name.
*
* @param classOrRecordDef node for class or record definition
*/
private void visitClassOrRecordDef(DetailAST classOrRecordDef) {
// we are not use inner classes because they can not
// have static methods
if (classDepth == 0) {
final DetailAST ident = classOrRecordDef.findFirstToken(TokenTypes.IDENT);
currentClass = packageName.getText() + "." + ident.getText();
classDepth++;
}
}
/**
* Checks method definition if this is
* {@code public static void main(String[])}.
*
* @param method method definition node
*/
private void visitMethodDef(DetailAST method) {
if (classDepth == 1
// method not in inner class or in interface definition
&& checkClassName()
&& checkName(method)
&& checkModifiers(method)
&& checkType(method)
&& checkParams(method)) {
log(method, MSG_KEY);
}
}
/**
* Checks that current class is not excluded.
*
* @return true if check passed, false otherwise
*/
private boolean checkClassName() {
return !excludedClasses.matcher(currentClass).find();
}
/**
* Checks that method name is @quot;main@quot;.
*
* @param method the METHOD_DEF node
* @return true if check passed, false otherwise
*/
private static boolean checkName(DetailAST method) {
final DetailAST ident = method.findFirstToken(TokenTypes.IDENT);
return "main".equals(ident.getText());
}
/**
* Checks that method has final and static modifiers.
*
* @param method the METHOD_DEF node
* @return true if check passed, false otherwise
*/
private static boolean checkModifiers(DetailAST method) {
final DetailAST modifiers =
method.findFirstToken(TokenTypes.MODIFIERS);
return modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) != null
&& modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) != null;
}
/**
* Checks that return type is {@code void}.
*
* @param method the METHOD_DEF node
* @return true if check passed, false otherwise
*/
private static boolean checkType(DetailAST method) {
final DetailAST type =
method.findFirstToken(TokenTypes.TYPE).getFirstChild();
return type.getType() == TokenTypes.LITERAL_VOID;
}
/**
* Checks that method has only {@code String[]} or only {@code String...} param.
*
* @param method the METHOD_DEF node
* @return true if check passed, false otherwise
*/
private static boolean checkParams(DetailAST method) {
boolean checkPassed = false;
final DetailAST params = method.findFirstToken(TokenTypes.PARAMETERS);
if (params.getChildCount() == 1) {
final DetailAST parameterType = params.getFirstChild().findFirstToken(TokenTypes.TYPE);
final boolean isArrayDeclaration =
parameterType.findFirstToken(TokenTypes.ARRAY_DECLARATOR) != null;
final Optional varargs = Optional.ofNullable(
params.getFirstChild().findFirstToken(TokenTypes.ELLIPSIS));
if (isArrayDeclaration || varargs.isPresent()) {
checkPassed = isStringType(parameterType.getFirstChild());
}
}
return checkPassed;
}
/**
* Whether the type is java.lang.String.
*
* @param typeAst the type to check.
* @return true, if the type is java.lang.String.
*/
private static boolean isStringType(DetailAST typeAst) {
final FullIdent type = FullIdent.createFullIdent(typeAst);
return STRING_PARAMETER_NAMES.contains(type.getText());
}
}
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