////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2017 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.design;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
/**
* Make sure that utility classes (classes that contain only static methods)
* do not have a public constructor.
* <p>
* Rationale: Instantiating utility classes does not make sense.
* A common mistake is forgetting to hide the default constructor.
* </p>
*
* @author lkuehne
*/
public class HideUtilityClassConstructorCheck extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "hide.utility.class";
@Override
public int[] getDefaultTokens() {
return getAcceptableTokens();
}
@Override
public int[] getAcceptableTokens() {
return new int[] {TokenTypes.CLASS_DEF};
}
@Override
public int[] getRequiredTokens() {
return getAcceptableTokens();
}
@Override
public void visitToken(DetailAST ast) {
// abstract class could not have private constructor
if (!isAbstract(ast)) {
final boolean hasStaticModifier = isStatic(ast);
final Details details = new Details(ast);
details.invoke();
final boolean hasDefaultCtor = details.isHasDefaultCtor();
final boolean hasPublicCtor = details.isHasPublicCtor();
final boolean hasMethodOrField = details.isHasMethodOrField();
final boolean hasNonStaticMethodOrField = details.isHasNonStaticMethodOrField();
final boolean hasNonPrivateStaticMethodOrField =
details.isHasNonPrivateStaticMethodOrField();
final boolean hasAccessibleCtor = hasDefaultCtor || hasPublicCtor;
// figure out if class extends java.lang.object directly
// keep it simple for now and get a 99% solution
final boolean extendsJlo =
ast.findFirstToken(TokenTypes.EXTENDS_CLAUSE) == null;
final boolean isUtilClass = extendsJlo && hasMethodOrField
&& !hasNonStaticMethodOrField && hasNonPrivateStaticMethodOrField;
if (isUtilClass && hasAccessibleCtor && !hasStaticModifier) {
log(ast.getLineNo(), ast.getColumnNo(), MSG_KEY);
}
}
}
/**
* @param ast class definition for check.
* @return true if a given class declared as abstract.
*/
private static boolean isAbstract(DetailAST ast) {
return ast.findFirstToken(TokenTypes.MODIFIERS)
.branchContains(TokenTypes.ABSTRACT);
}
/**
* @param ast class definition for check.
* @return true if a given class declared as static.
*/
private static boolean isStatic(DetailAST ast) {
return ast.findFirstToken(TokenTypes.MODIFIERS)
.branchContains(TokenTypes.LITERAL_STATIC);
}
/**
* Details of class that are required for validation.
*/
private static class Details {
/** Class ast. */
private final DetailAST ast;
/** Result of details gathering. */
private boolean hasMethodOrField;
/** Result of details gathering. */
private boolean hasNonStaticMethodOrField;
/** Result of details gathering. */
private boolean hasNonPrivateStaticMethodOrField;
/** Result of details gathering. */
private boolean hasDefaultCtor;
/** Result of details gathering. */
private boolean hasPublicCtor;
/**
* C-tor.
* @param ast class ast
* */
Details(DetailAST ast) {
this.ast = ast;
}
/**
* Getter.
* @return boolean
*/
public boolean isHasMethodOrField() {
return hasMethodOrField;
}
/**
* Getter.
* @return boolean
*/
public boolean isHasNonStaticMethodOrField() {
return hasNonStaticMethodOrField;
}
/**
* Getter.
* @return boolean
*/
public boolean isHasNonPrivateStaticMethodOrField() {
return hasNonPrivateStaticMethodOrField;
}
/**
* Getter.
* @return boolean
*/
public boolean isHasDefaultCtor() {
return hasDefaultCtor;
}
/**
* Getter.
* @return boolean
*/
public boolean isHasPublicCtor() {
return hasPublicCtor;
}
/**
* Main method to gather statistics.
*/
public void invoke() {
final DetailAST objBlock = ast.findFirstToken(TokenTypes.OBJBLOCK);
hasMethodOrField = false;
hasNonStaticMethodOrField = false;
hasNonPrivateStaticMethodOrField = false;
hasDefaultCtor = true;
hasPublicCtor = false;
DetailAST child = objBlock.getFirstChild();
while (child != null) {
final int type = child.getType();
if (type == TokenTypes.METHOD_DEF
|| type == TokenTypes.VARIABLE_DEF) {
hasMethodOrField = true;
final DetailAST modifiers =
child.findFirstToken(TokenTypes.MODIFIERS);
final boolean isStatic =
modifiers.branchContains(TokenTypes.LITERAL_STATIC);
final boolean isPrivate =
modifiers.branchContains(TokenTypes.LITERAL_PRIVATE);
if (!isStatic) {
hasNonStaticMethodOrField = true;
}
if (isStatic && !isPrivate) {
hasNonPrivateStaticMethodOrField = true;
}
}
if (type == TokenTypes.CTOR_DEF) {
hasDefaultCtor = false;
final DetailAST modifiers =
child.findFirstToken(TokenTypes.MODIFIERS);
if (!modifiers.branchContains(TokenTypes.LITERAL_PRIVATE)
&& !modifiers.branchContains(TokenTypes.LITERAL_PROTECTED)) {
// treat package visible as public
// for the purpose of this Check
hasPublicCtor = true;
}
}
child = child.getNextSibling();
}
}
}
}