001    /**
002     *   GRANITE DATA SERVICES
003     *   Copyright (C) 2006-2013 GRANITE DATA SERVICES S.A.S.
004     *
005     *   This file is part of the Granite Data Services Platform.
006     *
007     *   Granite Data Services is free software; you can redistribute it and/or
008     *   modify it under the terms of the GNU Lesser General Public
009     *   License as published by the Free Software Foundation; either
010     *   version 2.1 of the License, or (at your option) any later version.
011     *
012     *   Granite Data Services is distributed in the hope that it will be useful,
013     *   but WITHOUT ANY WARRANTY; without even the implied warranty of
014     *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
015     *   General Public License for more details.
016     *
017     *   You should have received a copy of the GNU Lesser General Public
018     *   License along with this library; if not, write to the Free Software
019     *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
020     *   USA, or see <http://www.gnu.org/licenses/>.
021     */
022    package org.granite.gravity.selector;
023    
024    /**
025     * An expression which performs an operation on two expression values.
026     *
027     * @version $Revision: 1.2 $
028     */
029    abstract public class BinaryExpression implements Expression {
030        protected Expression left;
031        protected Expression right;
032    
033        public BinaryExpression(Expression left, Expression right) {
034            this.left = left;
035            this.right = right;
036        }
037    
038        public Expression getLeft() {
039            return left;
040        }
041    
042        public Expression getRight() {
043            return right;
044        }
045    
046    
047        /**
048         * @see java.lang.Object#toString()
049         */
050        @Override
051        public String toString() {
052            return "(" + left.toString() + " " + getExpressionSymbol() + " " + right.toString() + ")";
053        }
054    
055        /**
056         * TODO: more efficient hashCode()
057         *
058         * @see java.lang.Object#hashCode()
059         */
060        @Override
061        public int hashCode() {
062            return toString().hashCode();
063        }
064    
065        /**
066         * TODO: more efficient hashCode()
067         *
068         * @see java.lang.Object#equals(java.lang.Object)
069         */
070        @Override
071        public boolean equals(Object o) {
072    
073            if (o == null || !this.getClass().equals(o.getClass())) {
074                return false;
075            }
076            return toString().equals(o.toString());
077    
078        }
079    
080        /**
081         * Returns the symbol that represents this binary expression.  For example, addition is
082         * represented by "+"
083         *
084         * @return the symbol
085         */
086        abstract public String getExpressionSymbol();
087    
088        /**
089         * @param expression
090         */
091        public void setRight(Expression expression) {
092            right = expression;
093        }
094    
095        /**
096         * @param expression
097         */
098        public void setLeft(Expression expression) {
099            left = expression;
100        }
101    
102    }