GenericsQueue.java

// A generic, fixed-size queue class.
class GenQueue<T> implements IGenQ<T> {
    private T[] q; // this array holds the queue
    private int putloc, getloc; // the put and get indices
    // Construct an empty queue with the given array.
    public GenQueue(T[] aRef) {
        q = aRef;
        putloc = getloc = 0;
    }
    // Put an item into the queue.
    public void put(T obj) throws QueueFullException {
        if(putloc == q.length)
            throw new QueueFullException(q.length);
        q[putloc++] = obj;
    }
    // Get a character from the queue.
    public T get() throws QueueEmptyException {
        if(getloc == putloc)
            throw new QueueEmptyException();
        return q[getloc++];
    }
}

public class GenericsQueue {
    public static void main(String[] args) {
        // Create an integer queue.
        Integer[] iStore = new Integer[10];
        GenQueue<Integer> q = new GenQueue<Integer>(iStore);
        Integer iVal;
        System.out.println("Demonstrate a queue of Integers.");
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("Adding " + i + " to q.");
                q.put(i); // add integer value to q
            }
        }
        catch (QueueFullException exc) {
            System.out.println(exc);
        }
        System.out.println();
        try {
            for (int i = 0; i < 5; i++) {
                System.out.print("Getting next Integer from q: ");
                iVal = q.get();
                System.out.println(iVal);
            }
        }
        catch (QueueEmptyException exc) {
            System.out.println(exc);
        }
        System.out.println();
        // Create a Double queue.
        Double[] dStore = new Double[10];
        GenQueue<Double> q2 = new GenQueue<Double>(dStore);
        Double dVal;
        System.out.println("Demonstrate a queue of Doubles.");
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("Adding " + (double)i/2 +
                        " to q2.");
                q2.put((double)i/2); // add double value to q2
            }
        }
        catch (QueueFullException exc) {
            System.out.println(exc);
        }
        System.out.println();
        try {
            for (int i = 0; i < 5; i++) {
                System.out.print("Getting next Double from q2: ");
                dVal = q2.get();
                System.out.println(dVal);
            }
        }
        catch (QueueEmptyException exc) {
            System.out.println(exc);
        }
    }
}