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     */
017    package org.apache.activemq.filter;
018    
019    
020    
021    /**
022     * An expression which performs an operation on two expression values.
023     * 
024     * 
025     */
026    public 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    }