calculator.java

基于算符优先关心的

/**
 * @Copyright(C) 2008 Software Engineering Laboratory (SELAB), Department of Computer 
 * Science, SUN YAT-SEN UNIVERSITY. All rights reserved.
**/

package parser;

import exceptions.*;

/**
 * Main program of the expression based calculator ExprEval
 * 
 * @author Yuanhang Yang   05373030
 * @version 2.00 (Last update:May,23th, 2008)
**/
public class Calculator
{
	/**function: calculate the result of the expression.
	 * 
	 * @param expression  user input to the calculator from GUI. 
	 * @return  if the expression is well-formed, return the evaluation result of it. 
	 * @throws ExpressionException  if the expression has error, a corresponding 
	 *                              exception will be raised. 
	**/
	public double calculate(String expression) throws ExpressionException
	{

		Parser p = new Parser(expression);
		return p.parse();
	}
}