public class WaitingQueue {
	private String[] waitingHere; 
	private int front; // "Leave a gap" when array is full
	private int back;  // back is the index AFTER last element
	
	private static final int ARR_LENGTH = 10;
	
	public WaitingQueue() {
		waitingHere = new String[ARR_LENGTH];
	}
	
	public boolean isEmpty() {
		return front == back;
	}
	
	// Returns true if Person is successfully added
	public boolean addAPerson(String newPerson) {
		if ((back + 1) % ARR_LENGTH == front) // array full
			return false;
		waitingHere[back] = newPerson;
		back = (back + 1) % ARR_LENGTH; // circular array behavior
		return true;
	}
	
	public String serveNextPerson() {
		if (isEmpty()) // empty queue
			return null;
		String firstPerson = waitingHere[front];
		waitingHere[front] = null; // optional
		front = (front + 1) % ARR_LENGTH;
		return firstPerson;
	}
	
	// Returns true if someone is removed from the queue
	public boolean leave(String personName) {
		
		// find first matching person
		boolean found = false;
		int position = front;
		while (position != back) { // pos may NOT be < back !!!
			if (waitingHere[position].equals(personName)) {
				waitingHere[position] = null; // optional
				found = true;
				break;
			}
			position = (position + 1) % ARR_LENGTH;
		}
		
		if (!found)
			return false;
		
		// left shift elements
		position = (position + 1) % ARR_LENGTH;
		while (position != back) {
			if (position != 0)
				waitingHere[position-1] = waitingHere[position];
			else
				waitingHere[ARR_LENGTH - 1] = waitingHere[0];
			position = (position + 1) % ARR_LENGTH;
		}
		
		// decrement back
		back = (back + ARR_LENGTH - 1) % ARR_LENGTH;
		return true;
	}
	
	public static void main(String[] args) {
		WaitingQueue q = new WaitingQueue();
		
		q.addAPerson("Person 1");
		q.addAPerson("Person 2");
		q.addAPerson("Person 3");
		q.addAPerson("Person 4");
		q.addAPerson("Person 5");
		q.addAPerson("Person 6");
		q.addAPerson("Person 7");
		q.addAPerson("Person 8");
		
		System.out.println(q.serveNextPerson());
		System.out.println(q.serveNextPerson());
		
		boolean b1 = q.leave("Person 2");
		boolean b2 = q.leave("Person 3");
		boolean b3 = q.leave("Person 4");
		
		System.out.println(b1);
		System.out.println(b2);
		System.out.println(b3);
		
		while (!q.isEmpty())
			System.out.println(q.serveNextPerson());
	}

}