ReturnNullInsteadOfBooleanCheck.java
////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2019 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.github.sevntu.checkstyle.checks.coding;
import java.util.ArrayDeque;
import java.util.Deque;
import com.github.sevntu.checkstyle.SevntuUtil;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
/**
* <p>
* It is a bad practice to use <code>Boolean</code> type for ternary logic. It
* is intended to be used for binary logic.
* </p>
*
* @author Ivan Sopov
* @since 1.8.0
*/
public class ReturnNullInsteadOfBooleanCheck extends AbstractCheck {
/**
* Warning message key.
*/
public static final String MSG_KEY = "return.null.Boolean";
/** Stack of states of the need in exploring the methods. */
private final Deque<Boolean> methodStack = new ArrayDeque<>();
/** Should we explore current method or not. */
private boolean exploreMethod;
@Override
public int[] getDefaultTokens() {
return new int[] {
TokenTypes.METHOD_DEF,
TokenTypes.LITERAL_RETURN,
};
}
@Override
public int[] getAcceptableTokens() {
return getDefaultTokens();
}
@Override
public int[] getRequiredTokens() {
return new int[] {
TokenTypes.METHOD_DEF,
};
}
@Override
public void beginTree(DetailAST rootAST) {
methodStack.clear();
}
@Override
public void visitToken(DetailAST ast) {
switch (ast.getType()) {
case TokenTypes.METHOD_DEF:
methodStack.push(exploreMethod);
final DetailAST returnTypeAST = ast
.findFirstToken(TokenTypes.TYPE).getFirstChild();
exploreMethod = "Boolean".equals(returnTypeAST.getText());
break;
case TokenTypes.LITERAL_RETURN:
if (exploreMethod) {
final DetailAST exprToken = ast
.findFirstToken(TokenTypes.EXPR).getFirstChild();
if ("null".equals(exprToken.getText())) {
log(ast, MSG_KEY);
}
}
break;
default:
SevntuUtil.reportInvalidToken(ast.getType());
break;
}
}
@Override
public void leaveToken(DetailAST ast) {
switch (ast.getType()) {
case TokenTypes.METHOD_DEF:
exploreMethod = methodStack.pop();
break;
case TokenTypes.LITERAL_RETURN:
// Do nothing
break;
default:
SevntuUtil.reportInvalidToken(ast.getType());
break;
}
}
}