A Generic Stack Driven by Commands

Problem

Write a generic class GenericStack<E> backed by a private ArrayList<E>, with:

void push(E item)
E pop() and E peek() — both throw IllegalStateException when the stack is empty
boolean isEmpty() and int size()
String toString() — the elements from top to bottom separated by single spaces, or empty when there are none

Then write a program that creates a GenericStack<String>, reads a number q and then q commands, one per line:

Command	Output
`push X`	nothing (`X` is a single word)
`pop`	`Popped: X`, or `Error: empty stack`
`peek`	`Top: X`, or `Error: empty stack`
`size`	`Size: n`

The program must catch the IllegalStateException to print the error message. After the last command, print Final (top first): followed by the stack's toString().

Input:

6
push red
push green
peek
pop
push blue
size

Output:

Top: green
Popped: green
Size: 2
Final (top first): blue red

Your solution

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