Queue.java Source code

Introduction

Here is the source code for Queue.java

Source

class Queue<E> {
    private E[] elements;
    private int head = 0, tail = 0;

    Queue(int size) {
        elements = (E[]) new Object[size];
    }

    void insert(E element) throws QueueFullException {
        if (isFull())
            throw new QueueFullException();
        elements[tail] = element;
        tail = (tail + 1) % elements.length;
    }

    E remove() throws QueueEmptyException {
        if (isEmpty()) {
            throw new QueueEmptyException();
        }
        E element = elements[head];
        head = (head + 1) % elements.length;
        return element;
    }

    boolean isEmpty() {
        return head == tail;
    }

    boolean isFull() {
        return (tail + 1) % elements.length == head;
    }
}

class QueueEmptyException extends Exception {
}

class QueueFullException extends Exception {
}

public class Main {
    public static void main(String[] args) throws QueueFullException, QueueEmptyException {
        Queue<String> queue = new Queue<String>(6);
        System.out.println("Empty: " + queue.isEmpty());
        System.out.println("Full: " + queue.isFull());
        queue.insert("A");
        queue.insert("B");
        queue.insert("C");
        queue.insert("D");
        queue.insert("E");
        System.out.println("Empty: " + queue.isEmpty());
        System.out.println("Full: " + queue.isFull());
        System.out.println("Removing " + queue.remove());
        System.out.println("Empty: " + queue.isEmpty());
        System.out.println("Full: " + queue.isFull());
        System.out.println("Adding F");
        queue.insert("F");
        while (!queue.isEmpty()) {
            System.out.println("Removing " + queue.remove());
        }

        System.out.println("Empty: " + queue.isEmpty());
        System.out.println("Full: " + queue.isFull());
    }
}