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added check for equals() vs. hashCode, RFE #554373 

see also Item 8 of "Bloch, Effective Java"
This commit is contained in:
Lars Kühne 2002-10-21 18:04:54 +00:00
parent dcca9953bc
commit fc24f5f8b6
4 changed files with 247 additions and 1 deletions
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144
src/checkstyle/com/puppycrawl/tools/checkstyle/checks/EqualsHashCodeCheck.java Normal file
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@ -0,0 +1,144 @@
////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2002 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;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import antlr.collections.AST;
import com.puppycrawl.tools.checkstyle.api.Check;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
/**
* Checks that classes that override equals() also override hashCode().
*
* <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>
* @author lkuehne
*/
public class EqualsHashCodeCheck
extends Check
{
// implementation note: we have to use the following members to
// keep track of definitions in different inner classes
/** maps OBJ_BLOCK to the method definition of equals() */
private final Map objBlockEquals = new HashMap();
/** maps OBJ_BLOCK to the method definition of equals() */
private final Set objBlockWithHashCode = new HashSet();
public int[] getDefaultTokens()
{
return new int[] {TokenTypes.METHOD_DEF};
}
public void beginTree()
{
objBlockEquals.clear();
objBlockWithHashCode.clear();
}
public void visitToken(DetailAST aAST)
{
// paranoia
if (aAST.getType() != TokenTypes.METHOD_DEF) {
return;
}
AST modifiers = aAST.getFirstChild();
final Set mods = new HashSet();
AST modifier = modifiers.getFirstChild();
while (modifier != null) {
mods.add(modifier.getText());
modifier = modifier.getNextSibling();
}
AST type = modifiers.getNextSibling();
AST methodName = type.getNextSibling();
DetailAST parameters = (DetailAST) methodName.getNextSibling();
if (type.getFirstChild().getType() == TokenTypes.LITERAL_BOOLEAN
&& "equals".equals(methodName.getText())
&& mods.contains("public")
&& parameters.getChildCount() == 1
&& isObjectParam(parameters.getFirstChild())
)
{
objBlockEquals.put(aAST.getParent(), aAST);
}
else if (type.getFirstChild().getType() == TokenTypes.LITERAL_INT
&& "hashCode".equals(methodName.getText())
// && modifiers.subTreeContains(TokenTypes.LITERAL_PUBLIC)
&& parameters.getFirstChild() == null) // no params
{
objBlockWithHashCode.add(aAST.getParent());
}
}
private boolean isObjectParam(AST aFirstChild)
{
if (aFirstChild.getType() != TokenTypes.PARAMETER_DEF) {
return false;
}
final AST modifiers = aFirstChild.getFirstChild();
AST type = modifiers.getNextSibling();
switch (type.getFirstChild().getType())
{
case TokenTypes.LITERAL_BOOLEAN:
case TokenTypes.LITERAL_BYTE:
case TokenTypes.LITERAL_CHAR:
case TokenTypes.LITERAL_DOUBLE:
case TokenTypes.LITERAL_FLOAT:
case TokenTypes.LITERAL_INT:
case TokenTypes.LITERAL_LONG:
case TokenTypes.LITERAL_SHORT:
return false;
default:
return true;
}
}
public void finishTree()
{
Set equalsDefs = objBlockEquals.keySet();
for (Iterator it = equalsDefs.iterator(); it.hasNext();) {
Object objBlock = it.next();
if (!objBlockWithHashCode.contains(objBlock)) {
DetailAST equalsAST = (DetailAST) objBlockEquals.get(objBlock);
log(equalsAST.getLineNo(), equalsAST.getColumnNo(),
"equals.noHashCode");
}
}
objBlockEquals.clear();
objBlockWithHashCode.clear();
}
}

3
src/checkstyle/com/puppycrawl/tools/checkstyle/checks/messages.properties
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@ -61,4 +61,5 @@ maxParam=More than {0,number,integer} parameters.
field.unused=''{0}'' is an unused field.
assignment.inner.avoid=Avoid inner assignments.
illegal.regexp=Line matches the illegal pattern ''{0}''.
equals.noHashCode=Definition of ''equals()'' without corresponding defnition of ''hashCode()''.

74
src/testinputs/com/puppycrawl/tools/checkstyle/InputSemantic.java
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@ -91,4 +91,78 @@ class InputSemantic
/** test **/
private static final long IGNORE = 666l + 666L;
void innerAssignments()
{
int a;
int b;
int c;
a = b = c = 1; // flag two inner assignments
String s = Integer.toString(b = 2); // flag inner assignment
Integer i = new Integer(a += 5); // flag inner assigment
c = b++; // common practice, don't flag
// even though technically an assigment to b
for (int j = 0; j < 6; j += 2) { // common practice, don't flag
a += j;
}
}
public class EqualsVsHashCode1
{
public boolean equals(int a) // wrong arg type, don't flag
{
return a == 1;
}
}
public class EqualsVsHashCode2
{
public boolean equals(String a) // flag
{
return true;
}
}
public class EqualsVsHashCode3
{
public boolean equals(Object a) // don't flag
{
return true;
}
public int hashCode()
{
return 0;
}
}
public class EqualsVsHashCode4
{
// in anon inner class
ByteArrayOutputStream bos1 = new ByteArrayOutputStream()
{
public boolean equals(Object a) // don't flag
{
return true;
}
public int hashCode()
{
return 0;
}
};
ByteArrayOutputStream bos2 = new ByteArrayOutputStream()
{
public boolean equals(Object a) // flag
{
return true;
}
};
}
}

27
src/tests/com/puppycrawl/tools/checkstyle/EqualsHashCodeCheckTest.java Normal file
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@ -0,0 +1,27 @@
package com.puppycrawl.tools.checkstyle;
import com.puppycrawl.tools.checkstyle.checks.EqualsHashCodeCheck;
public class EqualsHashCodeCheckTest
extends BaseCheckTestCase
{
public EqualsHashCodeCheckTest(String aName)
{
super(aName);
}
public void testIt() throws Exception
{
final CheckConfiguration checkConfig = new CheckConfiguration();
checkConfig.setClassname(EqualsHashCodeCheck.class.getName());
final Checker c = createChecker(checkConfig);
final String fname = getPath("InputSemantic.java");
final String[] expected = {
"125:9: Definition of 'equals()' without corresponding defnition of 'hashCode()'.",
"162:13: Definition of 'equals()' without corresponding defnition of 'hashCode()'.",
};
verify(c, fname, expected);
}
}