1. Implement a method which given a Stack will invert its contents. You can use any collection we’ve implemented so far to do so.

2. Suppose we have a postfix expression: 3 4 - 6 2 + *. Step by step show the contents of the stack as each token is processed.

3. Convert the following infix expression to postfix. Show all steps:

8 / 4 - 2 * 3 + 1

4. What is required for a class to be Iterable<E>?

5. What is required for a class to be an Iterator<E>?