FixedCapacityStack.java

Below is the syntax highlighted version of FixedCapacityStack.java from §1.3 Stacks and Queues.

/*************************************************************************
 *  Compilation:  javac FixedCapacityStack.java
 *  Execution:    java FixedCapacityStack
 *  
 *  Generic stack implementation with a fixed-size array.
 *
 *  % more tobe.txt 
 *  to be or not to - be - - that - - - is 
 * 
 *  % java FixedCapacityStack 5 < tobe.txt 
 *  to be not that or be
 *
 *  Remark:  bare-bones implementation. Does not do repeated
 *  doubling or null out empty array entries to avoid loitering.
 *
 *************************************************************************/

import java.util.Iterator;

public class FixedCapacityStack<Item> implements Iterable<Item> {
    private Item[] a;    // holds the items
    private int N;       // number of items in stack

    // create an empty stack with given capacity
    public FixedCapacityStack(int capacity) {
        a = (Item[]) new Object[capacity];   // no generic array creation
    }

    public boolean isEmpty()          {  return (N == 0);                  }
    public void push(Item item)       {  a[N++] = item;                    }
    public Item pop()                 {  return a[--N];                    }
    public Iterator<Item> iterator()  { return new ReverseArrayIterator(); }


    public class ReverseArrayIterator implements Iterator<Item> {
        private int i = N-1;

        public boolean hasNext() { return i >= 0; }
        public Item next()       { return a[i--]; }
        public void remove()     { throw new UnsupportedOperationException(); }
    }


    public static void main(String[] args) {
        int max = Integer.parseInt(args[0]);
        FixedCapacityStack<String> stack = new FixedCapacityStack<String>(max);
        while (!StdIn.isEmpty()) {
            String item = StdIn.readString();
            if (!item.equals("-")) stack.push(item); 
            else if (stack.isEmpty())  StdOut.println("BAD INPUT"); 
            else                       StdOut.print(stack.pop() + " ");
        }
        StdOut.println();

        // print what's left on the stack
        StdOut.print("Left on stack: ");
        for (String s : stack) {
            StdOut.print(s + " ");
        }
        StdOut.println();
    } 
}