////////////////////////////////////////////////////////////////////////////////
// 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.coding;
import java.util.HashMap;
import java.util.Map;
import antlr.collections.AST;
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;
import com.puppycrawl.tools.checkstyle.utils.CheckUtils;
/**
* <p>
* Checks that classes that either override {@code equals()} or {@code hashCode()} also
* overrides the other.
* This checks only verifies that the method declarations match {@link Object#equals(Object)} and
* {@link Object#hashCode()} exactly to be considered an override. This check does not verify
* invalid method names, parameters other than {@code Object}, or anything else.
* </p>
* <p>
* Rationale: The contract of equals() and hashCode() requires that
* equal objects have the same hashCode. Hence, whenever you override
* equals() you must override hashCode() to ensure that your class can
* be used in collections that are hash based.
* </p>
* <p>
* An example of how to configure the check is:
* </p>
* <pre>
* <module name="EqualsHashCode"/>
* </pre>
* @author lkuehne
*/
public class EqualsHashCodeCheck
extends AbstractCheck {
// implementation note: we have to use the following members to
// keep track of definitions in different inner classes
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY_HASHCODE = "equals.noHashCode";
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY_EQUALS = "equals.noEquals";
/** Maps OBJ_BLOCK to the method definition of equals(). */
private final Map<DetailAST, DetailAST> objBlockWithEquals = new HashMap<>();
/** Maps OBJ_BLOCKs to the method definition of hashCode(). */
private final Map<DetailAST, DetailAST> objBlockWithHashCode = new HashMap<>();
@Override
public int[] getDefaultTokens() {
return getAcceptableTokens();
}
@Override
public int[] getAcceptableTokens() {
return new int[] {TokenTypes.METHOD_DEF};
}
@Override
public int[] getRequiredTokens() {
return getAcceptableTokens();
}
@Override
public void beginTree(DetailAST rootAST) {
objBlockWithEquals.clear();
objBlockWithHashCode.clear();
}
@Override
public void visitToken(DetailAST ast) {
if (isEqualsMethod(ast)) {
objBlockWithEquals.put(ast.getParent(), ast);
}
else if (isHashCodeMethod(ast)) {
objBlockWithHashCode.put(ast.getParent(), ast);
}
}
/**
* Determines if an AST is a valid Equals method implementation.
*
* @param ast the AST to check
* @return true if the {code ast} is a Equals method.
*/
private static boolean isEqualsMethod(DetailAST ast) {
final DetailAST modifiers = ast.getFirstChild();
final DetailAST parameters = ast.findFirstToken(TokenTypes.PARAMETERS);
return CheckUtils.isEqualsMethod(ast)
&& modifiers.branchContains(TokenTypes.LITERAL_PUBLIC)
&& isObjectParam(parameters.getFirstChild())
&& (ast.branchContains(TokenTypes.SLIST)
|| modifiers.branchContains(TokenTypes.LITERAL_NATIVE));
}
/**
* Determines if an AST is a valid HashCode method implementation.
*
* @param ast the AST to check
* @return true if the {code ast} is a HashCode method.
*/
private static boolean isHashCodeMethod(DetailAST ast) {
final DetailAST modifiers = ast.getFirstChild();
final AST type = ast.findFirstToken(TokenTypes.TYPE);
final AST methodName = ast.findFirstToken(TokenTypes.IDENT);
final DetailAST parameters = ast.findFirstToken(TokenTypes.PARAMETERS);
return type.getFirstChild().getType() == TokenTypes.LITERAL_INT
&& "hashCode".equals(methodName.getText())
&& modifiers.branchContains(TokenTypes.LITERAL_PUBLIC)
&& !modifiers.branchContains(TokenTypes.LITERAL_STATIC)
&& parameters.getFirstChild() == null
&& (ast.branchContains(TokenTypes.SLIST)
|| modifiers.branchContains(TokenTypes.LITERAL_NATIVE));
}
/**
* Determines if an AST is a formal param of type Object.
* @param paramNode the AST to check
* @return true if firstChild is a parameter of an Object type.
*/
private static boolean isObjectParam(DetailAST paramNode) {
final DetailAST typeNode = paramNode.findFirstToken(TokenTypes.TYPE);
final FullIdent fullIdent = FullIdent.createFullIdentBelow(typeNode);
final String name = fullIdent.getText();
return "Object".equals(name) || "java.lang.Object".equals(name);
}
@Override
public void finishTree(DetailAST rootAST) {
objBlockWithEquals
.entrySet().stream().filter(detailASTDetailASTEntry -> {
return objBlockWithHashCode.remove(detailASTDetailASTEntry.getKey()) == null;
}).forEach(detailASTDetailASTEntry -> {
final DetailAST equalsAST = detailASTDetailASTEntry.getValue();
log(equalsAST.getLineNo(), equalsAST.getColumnNo(), MSG_KEY_HASHCODE);
});
objBlockWithHashCode.entrySet().forEach(detailASTDetailASTEntry -> {
final DetailAST equalsAST = detailASTDetailASTEntry.getValue();
log(equalsAST.getLineNo(), equalsAST.getColumnNo(), MSG_KEY_EQUALS);
});
objBlockWithEquals.clear();
objBlockWithHashCode.clear();
}
}