Design and implement a utility class "ExpressionSolver" to solve any good simple expression using the algorithm discussed in class. Simple expressions can have +,-,*,/, and parenthesis .

Write a driver program to read expressions from a text file ( one expression on each line) and print out the orginal expressions and their evaluated results on screen. Don't forget to prompt the user for the input filename.

Requirements:

- No advanced data structures( stack, queue, list,...)

- Error checking and user-friendliness are required

Things to turn in:

1) source code printouts- don't forget to comment your code

Not sure how to complete the program. Need to add more stuff on this one

public class ExpressionSolver

{

private static int index = 0;

private static String expression = "";

public static double solve(String exp)

{

index = 0;

expression = exp;

double r = 0;

double o1, o2, o3;

char op1, op2;

o1 = getOperand();

op1 = getOperator();

o2 = getOperand();

op2 = getOperator();

o3 = getOperand();

;

return(r);

}

private static double getOperand()

{

String s="";

double r;

while(expression.charAt(index) != '+' &&

expression.charAt(index) != '-' &&

expression.charAt(index) != '*' &&

expression.charAt(index) != '/' &&

index < expression.length()

)

{

s += expression.charAt(index);

index++;

}

r = Integer.parseInt(s);

System.out.println(r);

return r;

}

private static char getOperator()

{

char o;

o = expression.charAt(index);

index++;

System.out.println(o);

return o;

}

public static void main(

String[] args

)

{

// TODO Auto-generated method stub

System.out.println("1+2+3*4"

);

System.out.println( solve("1+2+3*4")

);

}

}