FixedCapacityStackOfStrings.java

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

/******************************************************************************
 *  Compilation:  javac FixedCapacityStackOfStrings.java
 *  Execution:    java FixedCapacityStackOfStrings
 *  Dependencies: StdIn.java StdOut.java
 *
 *  Stack of strings implementation with a fixed-size array.
 *
 *  % more tobe.txt
 *  to be or not to - be - - that - - - is
 *
 *  % java FixedCapacityStackOfStrings 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;
import java.util.NoSuchElementException;

public class FixedCapacityStackOfStrings implements Iterable<String> {
    private String[] a;  // holds the items
    private int n;       // number of items in stack

    // create an empty stack with given capacity
    public FixedCapacityStackOfStrings(int capacity) {
        a = new String[capacity];
        n = 0;
    }

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

    public boolean isFull() {
        return n == a.length;
    }

    public void push(String item) {
        a[n++] = item;
    }

    public String pop() {
        return a[--n];
    }

    public String peek() {
        return a[n-1];
    }

    public Iterator<String> iterator() {
        return new ReverseArrayIterator();
    }

    // an array iterator, in reverse order
    public class ReverseArrayIterator implements Iterator<String> {
        private int i = n-1;

        public boolean hasNext() {
            return i >= 0;
        }

        public String next() {
            if (!hasNext()) throw new NoSuchElementException();
            return a[i--];
        }
    }


    public static void main(String[] args) {
        int max = Integer.parseInt(args[0]);
        FixedCapacityStackOfStrings stack = new FixedCapacityStackOfStrings(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();
    }
}