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