A stack machine executes programs consisting of commands that manipulate an internal stack.
The stack is initially empty.
The commands are:
push N; push N onto the stack (N is any Double)
pop; removes top element from a stack
add; replace top two elements of the stack by their sum
mul; replace top two elements of the stack by their product
sub; replace top two elements of the stack by their difference:
[a, b, ... ] => [a-b, ... ]
div; replace top two elements of the stack by their quotient:
[a, b, ... ] => [a/b, ... ]

For example, the following program computes 23:
(push 1, push 2, mul, push 2, mul, push 2, mul)
The following types of exceptions are thrown by the stack machine:
stack empty
stack too short (not enough elements to complete the operation)
divide by 0
syntax error

(A) Implement a generic stack class for the stack machine:
class Stack { ??? }
Notes:
·You will need to implement the following methods: push, pop, top, clear, and toString.
·pop and top may throw EmptyStack exceptions
·How will you store the elements in the stack? List? Set?

(B) Implement your design using your solution for part 2.
Notes:
·Executing arithmetic commands may throw ShortStack exceptions if there aren't at least two elements on the stack.
·div may throw a DivByZero exception. Restore the stack before throwing this exception.
·Consider making the execute method and stack in your StackMachine class static. Then, commands can make static references to the stack without needing to have an association to the stack machine.
·The execute method of StackMachine should have separate catch clauses for each type of exception. For now it just prints the exception but in the future we could potentially have different strategies for each type of exception caught.
·After the last command is executed the stack machine should print the stack.
·Before the first command is executed the stack machine should clear the stack.