Collections笔记

Colletion是集合接口

Collections是集合工具类，是一个类哈！

public class CollectionsTest {

    public static void main(String[] args) {

        List list = new ArrayList();
        list.add(4);
        list.add(3);
        list.add(9);
        list.add(3);
        list.add(10);
        list.add(1);

        for (Iterator it = list.iterator() ; it.hasNext() ;){
            System.out.println(it.next());
        }
        //对list进行排序
        Collections.sort(list);

        System.out.println("------------");
        for (Iterator it = list.iterator() ; it.hasNext() ;){
            System.out.println(it.next());
        }

        Set set = new HashSet();
        set.add(3);
        set.add(10);
        set.add(199);
        set.add(1);
        set.add(44);
        set.add(199);
        //Sort方法不能对set排序，所以先把Set转换成List
        List l = new ArrayList(set);
        Collections.sort(l);
        System.out.println("------------");
        for (Iterator it = l.iterator() ; it.hasNext() ;){
            System.out.println(it.next());
        }

        //将ArrayList转换成线程安全的
        List syncList = Collections.synchronizedList(list);
    }
}

4
3
9
3
10
1
------------
1
3
3
4
9
10
------------
1
3
10
44
199