/**

* Book: Data Structures and Algorithms in Java, by Robert LaFore

* Chapter 4:

* queue.java

* demonstrates queue

* to compile this code: javac queue.java

* to run this program: java QueueApp

*/

class Queue {

private int maxSize;

private long[] queArray;

private int front;

private int rear;

private int nItems;

public Queue(int s) { // constructor

maxSize = s;

queArray = new long[maxSize];

front = 0;

rear = -1;

nItems = 0;

}

public void insert(long j) { // put item at rear of queue

if (rear == maxSize-1) // deal with wraparound

rear = -1;

queArray[++rear] = j; // increment rear and insert

nItems++; // one more item

}

public long remove() { // take item from front of queue

long temp = queArray[front++]; // get value and incr front

if (front == maxSize) // deal with wraparound

front = 0;

nItems--; // one less item

return temp;

}

public long peekFront() { // peek at front of queue

return queArray[front];

}

public boolean isEmpty() { // true if queue is empty

return (nItems==0);

}

public boolean isFull() { // true if queue is full

return (nItems==maxSize);

}

public int size() { // number of items in queue

return nItems;

}

} // end class Queue

class QueueApp {

public static void main(String[] args) {

Queue theQueue = new Queue(5); // queue holds 5 items

theQueue.insert(10); // insert 4 items

theQueue.insert(20);

theQueue.insert(30);

theQueue.insert(40);

theQueue.remove(); // remove 3 items

theQueue.remove(); // (10, 20, 30)

theQueue.remove();

theQueue.insert(50); // insert 4 more items

theQueue.insert(60); // (wraps around)

theQueue.insert(70);

theQueue.insert(80);

while (!theQueue.isEmpty()) { // remove and display all items

long n = theQueue.remove(); // (40, 50, 60, 70, 80)

System.out.print(n + " ");

}

System.out.println("");

}

}