broker-core/src/main/java/org/apache/qpid/server/filter/BinaryExpression.java

/**
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.qpid.server.filter;
//
// Based on like named file from r450141 of the Apache ActiveMQ project <http://www.activemq.org/site/home.html>
//

/**
 * An expression which performs an operation on two expression values.
 */
public abstract class BinaryExpression<T> implements Expression<T>
{
    private final Expression<T> left;
    private final Expression<T> right;

    public BinaryExpression(Expression<T> left, Expression<T> right)
    {
        this.left = left;
        this.right = right;
    }

    public Expression<T> getLeft()
    {
        return left;
    }

    public Expression<T> getRight()
    {
        return right;
    }

    /**
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString()
    {
        return "(" + left.toString() + " " + getExpressionSymbol() + " " + right.toString() + ")";
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode()
    {
        return toString().hashCode();
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object o)
    {

        if ((o == null) || !this.getClass().equals(o.getClass()))
        {
            return false;
        }

        return toString().equals(o.toString());

    }

    /**
     * Returns the symbol that represents this binary expression.  For example, addition is
     * represented by "+"
     *
     * @return the expression symbol
     */
    public abstract String getExpressionSymbol();

}