Thread: A Stack For Notation

Hello guys, I'm dealing with stacks and the general concept if pretty straightforward (FILO/LIFO). I'm using a stack to reformat an infix equation to postfix and prefix notation. I've seen several examples of this online, but I'd like to make it my own--so...

I've created a postfix class with the following method:

public void stackPF(String inString) throws PointerOutOfBoundException {
		inString = inString.trim();
		// Statements to evaluate array
		for (char ch : inString.toCharArray()) {
			// Evaluate equation in parenthesis
			System.out.println("Inside Loop");
			if (ch == '(') {
				System.out.println("paran");
				operatorStack.push(ch);
				do {
					if (ch >= 0 && ch <= 9) {
						operandStack.push(ch);
					} else {
						if (priority(ch) >= operatorStack.peek()) {
							operatorStack.push(ch);
						}
					}
				} while (ch != ')');
				//Pop characters within parenthesis
				System.out.println("End paran");
				operandStack.pop();
				operatorStack.pop();
			} else {
				if (ch >= 0 && ch <= 9) {
					System.out.println("No paran");
					operandStack.push(ch);
				}
				// Need to account for precedence!
				else if (ch == '+' || ch == '-' || ch == '/' || ch == '*') {
					System.out.println("Precedence");
					if(operatorStack.stackEmpty()){
						operatorStack.push(ch);
					}
					else if (priority(ch) >= operatorStack.peek()) {
						operatorStack.push(ch);
						operatorStack.pop();
					} else {
						operatorStack.push(ch);
					}
				}
			}
			size++;
		}
///Evaluate operators
	private static int priority(char ch) {
 
		switch (ch) {
		case '(' :
			return 0;
		case '-' : case '+':
			return 1;
		case '*' : case '/':
			return 2;
		}
		return -1;
	}

With this, I want to evaluate an equation within the parenthesis, and without parenthesis. In working out the details, I'm unsure whether or not it's necessary to create two separate stacks -- one for the operators and one for the operands. By doing it this way, I can empty the lists depending on parenthesis. The problem is when I enter (10+3)*9, I don't get any results and the program never records any of my values. Any ideas as to what might be causing this?

Within the stack class, I have the following methods (for clarity) in addition to others not here:

public T pop ( )
	{
		if (stackEmpty ( ))
		{
			System.out.println ("empty stack");
			return null;
		}
		else
		{
			T popped = (T) head.getData ( );
			head = head.getLink ( );
			return popped;
		}
	}
 
public void displayStack() throws PointerOutOfBoundException  {
 
		System.out.println("----------------");
		while(!empty()) {
			if(peek() != "(" ){
			System.out.print(" " + pop() + " ");
		} else {
			break;
		}
		System.out.println("\n----------------");
		}
	}

Thanks