Collections工具类（API）

public static void main(String[] args) {
    List<String> list = new ArrayList<>();
    Collections.addAll(list,"C++","Java","Python");//批量加元素
    System.out.println(list);
    Collections.shuffle(list);//打乱集合顺序 底层使用 Random 随机集合长度的索引 让随机索引与集合中的值进行交换
    System.out.println(list);
    List<Integer> list1 = new ArrayList<>();
    Collections.addAll(list1,2,3,4,8,1,2);
    Collections.sort(list1);//默认升序排序 值排序
    System.out.println(list1);

    List<People> list2 = new ArrayList<>();
   list2.add(new People("张三",23,175.3));
   list2.add(new People("李四",24,176.5));
   list2.add(new People("王五",27,178.5));
    //自定义比较规则对对象进行排序，也可以对象重写compareTo方法自定义比较规则
  Collections.sort(list2, (o1,  o2) ->Double.compare(o2.getHeight(), o1.getHeight()));
    System.out.println(list2);
}