Java类集.迭代器Iterator接口

//迭代器Iterator接口
	//判断是否有内容，有的话，就取出
	//只需要用Collection接口的iterator(),就能实例化Iterator接口
	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();//实例化Iterator接口
		while(iterator.hasNext()){//判断是否有内容
			Integer integer = iterator.next();
			System.out.println(integer);
		}
		
		//迭代器ListIterator接口,双向输出;由前往后，由后往前输出
		//谨记，要先，由前往后输出，才能由后往前输出
		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+",");
		}
	}