////////////////////////////////////////////////////////////////////////////////

 // checkstyle: Checks Java source code for adherence to a set of rules.

 // Copyright (C) 2001-2014  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.coding;

 import antlr.collections.AST;

 import com.google.common.collect.Maps;

 import com.google.common.collect.Sets;

 import com.puppycrawl.tools.checkstyle.api.Check;

 import com.puppycrawl.tools.checkstyle.api.DetailAST;

 import com.puppycrawl.tools.checkstyle.api.TokenTypes;

 import java.util.Map;

 import java.util.Set;

 /**

  * <p>

  * Checks that classes that override equals() also override hashCode().

  * </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 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<DetailAST, DetailAST> mObjBlockEquals = Maps.newHashMap();

     /** the set of OBJ_BLOCKs that contain a definition of hashCode() */

     private final Set<DetailAST> mObjBlockWithHashCode = Sets.newHashSet();

     @Override

     public int[] getDefaultTokens()

     {

         return new int[] {TokenTypes.METHOD_DEF};

     }

     @Override

     public void beginTree(DetailAST aRootAST)

     {

         mObjBlockEquals.clear();

         mObjBlockWithHashCode.clear();

     }

     @Override

     public void visitToken(DetailAST aAST)

     {

         final DetailAST modifiers = aAST.getFirstChild();

         final AST type = aAST.findFirstToken(TokenTypes.TYPE);

         final AST methodName = aAST.findFirstToken(TokenTypes.IDENT);

         final DetailAST parameters = aAST.findFirstToken(TokenTypes.PARAMETERS);

         if ((type.getFirstChild().getType() == TokenTypes.LITERAL_BOOLEAN)

                 && "equals".equals(methodName.getText())

                 && modifiers.branchContains(TokenTypes.LITERAL_PUBLIC)

                 && (parameters.getChildCount() == 1)

                 && isObjectParam(parameters.getFirstChild())

             )

         {

             mObjBlockEquals.put(aAST.getParent(), aAST);

         }

         else if ((type.getFirstChild().getType() == TokenTypes.LITERAL_INT)

                 && "hashCode".equals(methodName.getText())

                 && modifiers.branchContains(TokenTypes.LITERAL_PUBLIC)

                 && (parameters.getFirstChild() == null)) // no params

         {

             mObjBlockWithHashCode.add(aAST.getParent());

         }

     }

     /**

      * Determines if an AST is a formal param of type Object (or subclass).

      * @param aFirstChild the AST to check

      * @return true iff aFirstChild is a parameter of an Object type.

      */

     private boolean isObjectParam(AST aFirstChild)

     {

         final AST modifiers = aFirstChild.getFirstChild();

         final 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;

         }

     }

     @Override

     public void finishTree(DetailAST aRootAST)

     {

         final Set<DetailAST> equalsDefs = mObjBlockEquals.keySet();

         for (DetailAST objBlock : equalsDefs) {

             if (!mObjBlockWithHashCode.contains(objBlock)) {

                 final DetailAST equalsAST = mObjBlockEquals.get(objBlock);

                 log(equalsAST.getLineNo(), equalsAST.getColumnNo(),

                         "equals.noHashCode");

             }

         }

         mObjBlockEquals.clear();

         mObjBlockWithHashCode.clear();

     }

 }