@SuppressWarnings("unchecked")

public class SimpleQueue<Thing>{

Thing[] q;

int n = 0; // size of queue

int head = 0;

int tail = 0;

SimpleQueue(){

q = (Thing[]) new Object[1];

}

public void enqueue(Thing item){

if (n == q.length){

resize(2*n);

}

q[tail] = item;

tail++;

if (tail == q.length)

tail = 0;

n++;

}

public Thing dequeue(){

if (isEmpty())

return null;

Thing item = q[head];

q[head] = null;

head++;

if (head == q.length)

head = 0;

n--;

return item;

}

public boolean isEmpty(){

return n == 0;

}

public int size(){

return n;

}

public void resize(int newSize){

Thing[] newQ = (Thing[]) new Object[newSize];

for (int i = 0; i < n; i++){

newQ[i] = q[tail++];

if (tail == q.length)

tail = 0;

}

tail = n;

head = 0;

q = newQ;

}

}