001    /**
002     *
003     * Licensed to the Apache Software Foundation (ASF) under one or more
004     * contributor license agreements.  See the NOTICE file distributed with
005     * this work for additional information regarding copyright ownership.
006     * The ASF licenses this file to You under the Apache License, Version 2.0
007     * (the "License"); you may not use this file except in compliance with
008     * the License.  You may obtain a copy of the License at
009     *
010     * http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    package org.granite.gravity.selector;
019    
020    /**
021     * An expression which performs an operation on two expression values.
022     *
023     * @version $Revision: 1.2 $
024     */
025    abstract public class BinaryExpression implements Expression {
026        protected Expression left;
027        protected Expression right;
028    
029        public BinaryExpression(Expression left, Expression right) {
030            this.left = left;
031            this.right = right;
032        }
033    
034        public Expression getLeft() {
035            return left;
036        }
037    
038        public Expression getRight() {
039            return right;
040        }
041    
042    
043        /**
044         * @see java.lang.Object#toString()
045         */
046        @Override
047        public String toString() {
048            return "(" + left.toString() + " " + getExpressionSymbol() + " " + right.toString() + ")";
049        }
050    
051        /**
052         * TODO: more efficient hashCode()
053         *
054         * @see java.lang.Object#hashCode()
055         */
056        @Override
057        public int hashCode() {
058            return toString().hashCode();
059        }
060    
061        /**
062         * TODO: more efficient hashCode()
063         *
064         * @see java.lang.Object#equals(java.lang.Object)
065         */
066        @Override
067        public boolean equals(Object o) {
068    
069            if (o == null || !this.getClass().equals(o.getClass())) {
070                return false;
071            }
072            return toString().equals(o.toString());
073    
074        }
075    
076        /**
077         * Returns the symbol that represents this binary expression.  For example, addition is
078         * represented by "+"
079         *
080         * @return the symbol
081         */
082        abstract public String getExpressionSymbol();
083    
084        /**
085         * @param expression
086         */
087        public void setRight(Expression expression) {
088            right = expression;
089        }
090    
091        /**
092         * @param expression
093         */
094        public void setLeft(Expression expression) {
095            left = expression;
096        }
097    
098    }