below is some of the work i began on LispEvaluate on java. but i'm having a hard time figuring out the rest of the work i need to do. please help me

package lisp;

import java.util.Scanner;

import stack.*;

/**

* The lispCalculate method takes a valid arithmetic

* Lisp expression and evaluates it to calculate the numeric

* output. This code must be provided by you, and will

* make use of stacks.

*

*/

public class LispEvaluate {

/**

* Sets up a loop that treats entered user inputs from the console as Lisp

* expressions, then computes and prints their values. Behavior for badly

* formatted Lisp expressions is not defined, but will likely cause the code

* to crash or otherwise misbehave.

*

* @param args Ignored

*/

public static void main(String[] args) {

Scanner console = new Scanner(System.in);

String input = "";

while(true) {

System.out.print("Enter a Lisp expression or use \"q\" or \"quit\" to exit the program: ");

input = console.nextLine();

if(input.equals("q") || input.equals("quit")) break; // Exit the loop

System.out.println("Evaluates to: " + lispCalculate(input));

}

System.out.println("Goodbye");

console.close();

}

/**

* Given a String containing a valid Lisp expression using only

* the operators +, -, /, and *, evaluate the expression and

* return the result.

*

* NOTE: You are NOT allowed to use arrays or ArrayLists. Your algorithm(s)

* should be based on stacks.

*

* @param lispExpression Valid arithmetic Lisp expression.

* @return Numeric result of evaluating the Lisp expression.

*/

public static double lispCalculate(String lispExpression) {

String spacedOut = addSpaces(lispExpression); // Adds extra white space around parentheses

String postfixSpaced = prefixToPostfix(spacedOut); // Converts spaced prefix Lisp expression to spaced postfix Lisp expression

return calculateSpacedPostfix(postfixSpaced); // Calculates the numeric result from processing the spaced postfix Lisp expression

}

///// You MUST provide complete and correctly formatted Javadoc comments to all methods below this point /////

private static String addSpaces(String lispExpression) {

String result = "";

for(int i = 0; i < lispExpression.length(); i++) {

char c = lispExpression.charAt(i);

switch(c) {

case '(':

result += " ( "; // put spaces around (

break;

//more

default:

result += c;

}

}

return result;

}

private static String prefixToPostfix(String spacedOut) {

StackInterface operators = new LinkedStack<>();

String result = "";

Scanner scan = new Scanner(spacedOut);

while(scan.hasNext()) {

String token = scan.next();

switch(token) {

case "+": case "-": case "/": case "*":

operators.push(token);

break;

case "(":

// MORE? WHAT TO DO HERE?

break;

case ")":

result += " " + operators.pop() + " ) ";

break;

default:

result += " " + token + " ";

}

}

scan.close();

return result;

}

private static double calculateSpacedPostfix(String postfixSpaced) {

Scanner scan = new Scanner(postfixSpaced);

StackInterface operands = new LinkedStack<>();

while(scan.hasNext()) {

String token = scan.next();

switch(token) {

case "+":

//TODO

break;

case "(":

break;

case ")":

//ANYTHING HERE

break;

default:

double value = Double.parseDouble(token);

operands.push(value); // Put each operand on the stack

}

}

scan.close();

return 0;

}

}