List遍历时对List元素的操作——ListIterator

public class TestList {
    public static void main(String[] args){
        List list = new ArrayList();
        list.add("a1");
        list.add("a2");
        list.add("a3");
        list.add("a4");
        ListIterator it = list.listIterator();
        //list特有的ListIterator迭代器，遍历时候可以对list进行增删查改
        while (it.hasNext()){//正序遍历
            Object object = it.next();//it.next 不能出现超过一次
            if(object.equals("a1")){
                it.add("a5");//增加
            }
            if(object.equals("a2")){
                it.set("a6");//修改
            }
            if(object.equals("a3")){
                it.remove();//删除
            }
        }
        System.out.println(list);
        StringBuilder sb = new StringBuilder();
        ListIterator it2 = list.listIterator(list.size()); //list.size相当于是指针
        while (it2.hasPrevious()){//倒序遍历
            Object object = it2.previous();
            sb.append(object+",");

        }
        System.out.println("ches"+sb.toString());
    }
}