Java:Evaluation of Mathematical Expression only from left to right only.

I have written a Java program which evaluates a mathematical expression from left to right only.however im stuck up with the output.Im not getting the desired output.
Please Note: There is no precedence in operators(evaluation should be from LEFT->RIGHT.)

Code :

/*
 * Created on Jul 10, 2011
 *
 * To change the template for this generated file go to
 * Window&gt;Preferences&gt;Java&gt;Code Generation&gt;Code and Comments
 */
package com.comcast;
import java.util.*;
public class Evaluation
{
    private static final char[] validOperators = {'/','*','+','-'};
 
	private Evaluation()
	{
		 /* Using a private contructor to prevent instantiation
			 Using class as a simple static utility class
		 */
	}
 
	private static int evaluate(String leftSide, char oper, String rightSide)
	 throws IllegalArgumentException
	{
		System.out.println("Evaluating: " + leftSide +  " (" + oper + ") " + rightSide);
		int total = 0;
		int leftResult = 0;
		int rightResult = 0;
		String originalString =leftSide;
		int operatorLoc  = findOperatorLocation(leftSide);
		leftSide = leftSide.substring(0,operatorLoc);
		rightSide = originalString.substring(operatorLoc+1,operatorLoc+2);
		String remainingString = originalString.substring(operatorLoc+2,originalString.length());
 
 
		System.out.println("leftSide -->"+leftSide);
		System.out.println("rightSide -->"+rightSide);
		System.out.println("remainingString --->"+remainingString);
 
	 try{
			 leftResult = Integer.parseInt(leftSide);
		}catch(Exception e){
				throw new IllegalArgumentException("Invalid value found in portion of equation: "
				  + leftSide);
	    }
 
 
	 try{
			 rightResult = Integer.parseInt(rightSide);
	   }catch(Exception e){
				throw new IllegalArgumentException("Invalid value found in portion of equation: "
				  + rightSide);
	   }
 
 
		System.out.println("Getting result of: " + leftResult + " " + oper + " " + rightResult);
		switch(oper)
		{
			case '/':
			 total = leftResult / rightResult; break;
			case '*':
			 total = leftResult * rightResult; break;
			case '+':
			 total = leftResult + rightResult; break;
			case '-':
			 total = leftResult - rightResult; break;
			default:
			 throw new IllegalArgumentException("Unknown operator.");
		}
		System.out.println("Returning a result of: " + total);
		String totally = String.valueOf(total)+remainingString;
		return evaluate(totally,findCharacter(totally),remainingString);
	}
 
	private static int findOperatorLocation(String string)
		{
			int index = -1;			
				index = string.indexOf(string.substring(1,2));			    
				if(index >= 0){				
				 return index;
				}
			return index;
		}
 
	private static char findCharacter(String string){
 
		char c='\u0000';  
		int index = -1;			
						index = string.indexOf(string.substring(1,2));
						if(index >= 0){				
						 c = string.charAt(index);
						 return c;
						} 		 			 	
		 return c;	
	}
 
	public static int processEquation(String equation)
	  throws IllegalArgumentException
	{
		  return evaluate(equation,'+',"0");
	}
 
	public static void main(String[] args)
	{
		//String usage = "Usage: java MathParser equation\nWhere equation is a series"
		// + " of integers separated by valid operators (+,-,/,*)";
 
		//if(args.length < 1 || args[0].length() == 0)
		// System.out.println(usage);
		Scanner input = new Scanner(System.in); 
		System.out.print("Enter the equation to be evaluated ");
 
		String equation = (String)input.next();
			int result = Evaluation.processEquation(equation);
		 System.out.println("The result of your equation ("
			   + equation + ") is: " + result);
 
		//catch(IllegalArgumentException iae)
		//{
		//	System.out.println(iae.getMessage() + "\n" + usage);
		//}
	}
}

Expression Input:3+5*2-5 =>3+5*2-5 =>8*2-5 =>16-5 =>Expected Output :11

im getting as below output Enter the equation to be evaluated 3+5*2-5
Evaluating: 3+5*2-5 (+) 0
leftSide -->3
rightSide -->5
remainingString --->*2-5
Getting result of: 3 + 5
Returning a result of: 8
Evaluating: 8*2-5 ( * ) *2-5
leftSide -->8
rightSide -->2
remainingString --->-5
Getting result of: 8 * 2
Returning a result of: 16
Evaluating: 16-5 (6) -5
leftSide -->1
rightSide -->-
remainingString --->5
Exception in thread "main" java.lang.IllegalArgumentException: Invalid value found in portion of equation: -
at Evaluation.evaluate(Evaluation.java:49)
at Evaluation.evaluate(Evaluation.java:70)
at Evaluation.evaluate(Evaluation.java:70)
at Evaluation.processEquation(Evaluation.java:98)
at Evaluation.main(Evaluation.java:112)

Im unable to make my program generic for any equation entered.Help provided will be appreciated.Please note this is not a homework question.
Need help !!!!!Code fix required for the above program