Algs4-1.3不定容泛型栈（不可迭代）

 public class FixedCapacityStack<Item>
{
    private Item[] a;
    private int N;
    public FixedCapacityStack(int cap)
    {a=(Item[]) new Object[cap];}
   
    public void push(Item item)
    {
        if(N==a.length) resize(2*a.length);
        a[N++]=item;
    }
   
    public Item pop()
    {
        Item item= a[--N];
        a[N]=null;
        if(N>0 && N==a.length/4)  resize(a.length/2);
        return item;
    }
   
    public boolean isEmpty()
    {return N==0;}
   
    public int size()
    {return N;}
   
    private void resize(int max)
    {
        Item[] temp=(Item[]) new Object[max];
        for(int i=0;i<N;i++)
             temp[i]=a[i];
        a=temp;
    }
   
   
    public static void main(String[] args)
    {
        FixedCapacityStack<String> s;
        s=new FixedCapacityStack<String>(Integer.parseInt(args[0]));
        while(!StdIn.isEmpty())
        {
            String item=StdIn.readString();
            if(!item.equals("-"))
                s.push(item);
            else if (!s.isEmpty())
                StdOut.printf(s.pop()+" ");
        }//end while
        StdOut.println("("+s.size()+" left on stack)");
    }//end main
}//end class