Build the Array Stack Core

The two fields are declared but nothing sets them up, so a new stack is unusable. The given isEmpty(), isFull() and toString() show exactly how items and top are meant to behave - read them and make the rest agree.

Requirements:
1. In the constructor, give items room for MAX_SIZE values and set top to the value that means empty.
2. Write push(int) returning false when full and true otherwise, pop() and peek() returning -1 when empty, and size() returning how many values are stored.

Do NOT write a main method.