Java class set. Iterator interface Iterator

//Iterator Iterator interface
	/ / Determine whether there is content, if there is, take it out
	//Just use the iterator() of the Collection interface to instantiate the Iterator interface
	public static void main(String[] args) {
		List<Integer> arrayList = new ArrayList<Integer>();
		arrayList.add(1);
		arrayList.add(2);
		arrayList.add(3);
		
		Iterator<Integer> iterator = arrayList.iterator();//Instantiate the Iterator interface
		while(iterator.hasNext()){//Determine whether there is content
			Integer integer = iterator.next();
			System.out.println(integer);
		}
		
		//Iterator ListIterator interface, bidirectional output; output from front to back, from back to front
		//Remember, you must first, output from front to back before you can output from back to front
		ListIterator>Integer> listIterator = arrayList.listIterator ();
		while (listIterator.hasNext()) {
			Integer integer = listIterator.next();
			System.out.print(integer+",");
		}
		
		System.out.println();
		
		while (listIterator.hasPrevious()) {
			Integer previous = listIterator.previous();
			System.out.print(previous+",");
		}
	}