PersonQ.java

public class PersonQ {
    private Person [] q;
    private int size;
    private int total;
    private int front;
    private int rear;

    public PersonQ() {
        size = 100;
        total = 0;
        front = 0;
        rear = 0;
        q = new Person[size];
    }

    public PersonQ(int size) {
        this.size = size;
        total = 0;
        front = 0;
        rear = 0;
        q = new Person[size];
    }

    public boolean enqueue(Person item) {
        if (isFull()) {
            return false;
        } else {
            total++;
            q[rear] = item;
            //rear++; there is a problem!!
            rear = (rear + 1) % size;//in order to back to
            return true;
        }
    }


    public Person dequeue() {
        Person item = q[front];
        total--;
        //front ++; there is a problem too
        front = (front + 1) % size;
        return item;
    }

    public boolean isFull() {
        if (size == total) {
            return true;
        } else {
            return false;
        }
    }

    public void showAll() {
        int f = front;
        if (total != 0) {
            for (int i = 0; i < total; i++) {
                System.out.println("" + q[f]);
                f = (f + 1) % size;
            }
        }
    }
}