////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2008 Oliver Burn
//
// 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.Check;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
/**
* 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
* @version $Revision: 1.12 $
*/
public class HideUtilityClassConstructorCheck extends Check
{
@Override
public int[] getDefaultTokens()
{
return new int[] {TokenTypes.CLASS_DEF};
}
@Override
public void visitToken(DetailAST aAST)
{
final DetailAST objBlock = aAST.findFirstToken(TokenTypes.OBJBLOCK);
DetailAST child = (DetailAST) objBlock.getFirstChild();
boolean hasMethodOrField = false;
boolean hasNonStaticMethodOrField = false;
boolean hasDefaultCtor = true;
boolean hasPublicCtor = false;
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 && !isPrivate) {
hasNonStaticMethodOrField = 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 = (DetailAST) child.getNextSibling();
}
final boolean hasAccessibleCtor = (hasDefaultCtor || hasPublicCtor);
// figure out if class extends java.lang.object directly
// keep it simple for now and get a 99% solution
// TODO: check for "extends java.lang.Object" and "extends Object"
// consider "import org.omg.CORBA.*"
final boolean extendsJLO = // J.Lo even made it into in our sources :-)
aAST.findFirstToken(TokenTypes.EXTENDS_CLAUSE) == null;
final boolean isUtilClass =
extendsJLO && hasMethodOrField && !hasNonStaticMethodOrField;
if (isUtilClass && hasAccessibleCtor) {
log(aAST.getLineNo(), aAST.getColumnNo(), "hide.utility.class");
}
}
}