Question

1) [100] Write an array-based implementation of a Queue (generic version) as the data structure and the Queuelnterface defined on page 415 of the textbook. Also use the class QueueException defined on the same page to catch all appropriate exceptions. To test you program, create a separate test class and add 15 unique integers to the queue. Create the following methods in the TEST class which will use the public methods of the Queue to provide the following functions: a) displayQueue() method that prints the contents of the Queue but leaves the Queue in the same state once it has finished (Hint: you need to add a marker). b) countQueueditems() method that counts the number of items in the Queue but does not change the Queue (your queue should not have a size() method - and if it does, you can not use it). c) sumQueueditems() method that adds all the integers in the Queue but does not change the Queue.

Book - Data abstraction and problem-solving with Java - Walls and Mirrors 3rd edition

Language - Java

Answer 1

program code to copy

Test.java

public class Test 
{

    private static Queue<Integer> queue;

    public static void main(String[] args) 
        {
        queue = new Queue();
        for (int i = 0; i < 15; i++) 
                {
            queue.enqueue(i);
        }

        displayQueue();
        System.out.println("\nCount: " +countQueuedItems());
        System.out.println("Sum: " + sumQueuedItems());
        System.out.println("Max: " + maxQueuedItem());
        System.out.println("Min: " + minQueuedItem());
    }

    public static void displayQueue() 
        {
        Integer last = queue.dequeue();
        System.out.println(last);
        queue.enqueue(last);
        Integer item;
        while ((item = queue.dequeue()) != last) 
                {
            System.out.println(item);
            queue.enqueue(item);
        }
        queue.enqueue(last);
    }

    public static int countQueuedItems() 
        {
        Integer last = queue.dequeue();
        queue.enqueue(last);
        int count = 1;
        Integer item;
        while ((item = queue.dequeue()) != last) 
                {
            queue.enqueue(item);
            count++;
        }
        queue.enqueue(last);
        return count;
    }

    public static int sumQueuedItems() 
        {
        Integer last = queue.dequeue();
        queue.enqueue(last);
        int sum = last;
        Integer item;
        while ((item = queue.dequeue()) != last) 
                {
            sum += item;
            queue.enqueue(item);
        }
        queue.enqueue(last);
        return sum;
    }

    public static int maxQueuedItem() 
        {
        Integer last = queue.dequeue();
        queue.enqueue(last);
        int max = last;
        Integer item;
        while ((item = queue.dequeue()) != last) 
                {
            if(item > max)
                max = item;
            queue.enqueue(item);
        }
        queue.enqueue(last);
        return max;
    }

    public static int minQueuedItem() 
        {
        Integer last = queue.dequeue();
        queue.enqueue(last);
        int min = last;
        Integer item;
        while ((item = queue.dequeue()) != last) 
                {
            if(item < min)
                min = item;
            queue.enqueue(item);
        }
        queue.enqueue(last);
        return min;
    }
}


============================================================================

Queue.java

public class Queue<T> implements QueueInterface<T> 
{
    private Node lastNode;

    private class Node 
        {
        private T item;
        private Node next;

        Node(T item, Node next) 
                {
            this.item = item;
            this.next = next;
        }

    }

    public Queue() 
        {
        lastNode = null;
    }

    public boolean isEmpty() 
        {
        return lastNode == null;
    }

    public void enqueue(T item) 
        {
        Node newNode = new Node(item, null);
        if (isEmpty()) 
                {
            newNode.next = newNode;
        }
        else 
                {
            newNode.next = lastNode.next;
            lastNode.next = newNode;
        }
        lastNode = newNode;
    }

    public T dequeue() 
        {
        if (isEmpty()) throw new QueueException("Queue is empty");
        Node firstNode = lastNode.next;
        if(firstNode == lastNode) lastNode = null;
        else lastNode.next = firstNode.next;
        return firstNode.item;
    }

    public void dequeueAll() 
        {
        lastNode = null;
    }

    public T peek() 
        {
        if(isEmpty()) throw new QueueException("Queue is empty");
        return lastNode.item;
    }
}

====================================================================

QueueInterface.java


public interface QueueInterface<T> 
{
    boolean isEmpty();

    void enqueue(T item);

    T dequeue() throws QueueException;

    void dequeueAll();

    T peek();

}


=====================================================

QueueException.java


public class QueueException extends RuntimeException 
{
    public QueueException(String message) 
        {
        super(message);
    }
}

sample output

Problems @ Javadoc B. Declaration Console X <terminated Test [Java Application] C:\Program Files\Java\jrel.8.O_201\bin\javaw.exe (Jul 31, 2020, 9:43:23 PM) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Count: 15 Sum: 105 Max: 14 Min: 0