StackArray.java

/*  Name:    Rafael Neves Moraes
 *
 *  Description:  Stack algorithm Object Implementation.
 *
 *  Written:       5/06/2019
 *
 *  % javac StackArray.java
 *  % java StackArray
 *  Uses between ~ 8 N and ~ 32 N  bytes to represent a stackwith N items
 *
 **************************************************************************** */
public class StackArray<Item>
{

    private Item[] s;
    private int N = 0;

    public FixedCapacityStackOfStrings(int capacity)
    {
        s = new Item[capacity];
    }

    public boolean isEmpty()
    {
        return N == 0;
    }

    public void push(Item item)
    {
        if (N == s.length) resize(2 * s.length);
        s[N++] = item;
    }

    public Item pop()
    {
        Item item = s[--N];
        s[N] = null;
        return item;
    }

    public ResizingArrayStackOfStrings()
    {
        s = new Item[1];
    }

    private void resize(int capacity)
    {
        Item[] copy = new Item[capacity];
        for (int i = 0; i < N; i++)       copy[i] = s[i];
        s = copy;
    }

}