private void ensureCapacity(int size){
		int capacity = elements.length;
		if(size < capacity ){
			return;
		}else{
			capacity = capacity << 1;
		}
		Comparable<?super E>[] newElement = new Comparable[capacity];
		System.arraycopy(elements, 0, newElement, 0, elements.length);
		elements = newElement;
	}