private static void stackOperation(IStack stack) {
		do {
			System.out.println("---------------------------------------------------------------------------------------");			
			System.out.println("[1] capcity / [2] clear / [3] isEmpty / [4] peek / [5] size / [6] pop / [7] push / [8] toString");
			System.out.println("---------------------------------------------------------------------------------------");
			
			inputStack = scanner.next();

			switch (inputStack.charAt(0)) {
			case '1':
				System.out.println("Capacity: " + stack.capacity());
				break;
			case '2':
				stack.clear();
				System.out.println("Cleared!");				
				break;
			case '3':
				System.out.println("Is empty: " + stack.isEmpty());				
				break;
			case '4':
				System.out.println("Peek: " + stack.peek());
				break;
			case '5':
				System.out.println("Size: " + stack.size());			
				break;
			case '6':
				System.out.println("Popped: " + stack.pop());
				break;
			case '7':
				System.out.println("Enter value: ");
				input = scanner.next();
				System.out.println("Enqueued: " + stack.push(new StringNode(input)));					
				break;
			case '8':
				System.out.println(stack.toString());
				break;				
			}
		} while (!inputStack.equals("exit"));
		inputImpl = "exit";
	}