GenericArrayListQueue.java

import java.util.ArrayList;

public class GenericArrayListQueue<T> {
 ArrayList<T> _queue = new ArrayList<T>();

 private boolean hasElements() {
 return !_queue.isEmpty();
 }

 public T peek() {
 T result = null;
 if(this.hasElements()) { result = _queue.get(0); }
 return result;
 }

 public boolean add(T element) {
 return _queue.add(element);
 }

 public T poll() {
 T result = null;
 if(this.hasElements()) { result = _queue.remove(0); }
 return result;
 }

 public static void main(String[] args) {
 GenericArrayListQueue<Integer> queue = new GenericArrayListQueue<Integer>();
 System.out.println("Running...");
 assert queue.peek() == null;
 assert queue.poll() == null;
 assert queue.add(1) == true;
 assert queue.peek() == 1;
 assert queue.add(2) == true;
 assert queue.peek() == 1;
 assert queue.poll() == 1;
 assert queue.peek() == 2;
 assert queue.poll() == 2;
 assert queue.peek() == null;
 assert queue.poll() == null;
 System.out.println("Finished.");
 }
}