StaticQueue.java

package br.unisinos.queue;

public class StaticQueue<E> implements Queue<E> {

	protected int first;
	protected int last;
	protected E elements[];

	@SuppressWarnings("unchecked")
	public StaticQueue(int maxSize) {
		elements = (E[]) new Object[maxSize];
		first = last = -1;
	}

	public boolean isEmpty() {
		return first == -1;
	}

	public boolean isFull() {
		return first == ((last + 1) % elements.length);
	}

	public int numElements() {
		if (isEmpty())
			return 0;
		else {
			int n = elements.length;
			return ((n + last - first) % n) + 1;
		}
	}

	public E front() throws UnderflowException {
		if (isEmpty())
			throw new UnderflowException();
		return elements[first];
	}

	public E back() throws UnderflowException {
		if (isEmpty())
			throw new UnderflowException();
		return elements[last];
	}

	public void enqueue(E element) throws OverflowException {
		if (isFull())
			throw new OverflowException();
		else {
			if (last == -1)
				first = last = 0;
			else
				last = (last + 1) % elements.length;
			elements[last] = element;
		}
	}

	public E dequeue() throws UnderflowException {
		if (isEmpty())
			throw new UnderflowException();
		E element = elements[first];
		elements[first] = null;
		if (first == last)
			first = last = -1;
		else
			first = (first + 1) % elements.length;
		return element;
	}

	public String toString() {
		if (isEmpty())
			return "[Empty]";
		else {
			String s = "[" + elements[first];
			int n = numElements();
			for (int i = 1; i < n; i++) {
				int k = (first + i) % elements.length;
				s += ", " + elements[k];
			}
			return s + "]";
		}
	}

}