Perform these steps:

1) Implement a list-based stack of chars as follows:
   a) Create a StackNode class that will be the basis for the linked list.
      Each StackNode will hold a single char and a next pointer.
   b) Create a MyStack class that will implement these methods:
   	- constructor (create an empty stack)
   	- isEmpty() returns true if stack is empty
   	- push(char ch) puts the char ch on the stack
   	- char pop() removes the top element of the stack and returns it
   c) Write a short program (main) to test it.


2) Write a method called checkParens() that accepts a String as a parameter.
It will use a stack to determine whether or not the given string has properly
matched ()’s. IMPORTANT: The checkParens() method will NOT be inside MyStack ...
it will be a separate static method (in the driver).

checkParens() should return false for strings like these:
((hi there)
(hi there)) how are( you?

And it should return true for strings like these:
(hi there)
(hi there (how)(are)(you (doing (today))) now).

The basic idea is that we push (‘s on the stack when we encounter then and we
pop the elements on the stack when we see a “)”. If we see a “)” and the stack
is empty then there is a close without a matching open. If we reach the end of
the string and there are still characters on the stack then there were extra “(“
characters.


3) If you have time then take a look at the built-in Java stack commands and
utilize the built-in stack rather than your own. (https://docs.oracle.com/javase/7/docs/api/java/util/Stack.html)