Collections类及常用 API

//注意：Collection值接口，Collections是类class CollectionDemo1{
    public static void fun1(){
        List<String> str=new ArrayList<>();
        str.add("zhangsan");
        str.add("wangwu");
        str.add("liliu");
        System.out.println("交换顺序之前:");
        for (String string : str) {
            System.out.println(string+" ");
        }
        System.out.println();
        Collections.swap(str, 1, 2);
        System.out.println("交换顺序之后：");
        for (String string : str) {
            System.out.println(string+" ");
        }
        System.out.println();
        Collections.sort(str);
        System.out.println("按照自然顺序排列：");//会按照字符串的顺序排列
        for (String string : str) {
            System.out.println(string+" ");
        }
        System.out.println("二分法查找：");
        int s = Collections.binarySearch(str, "wangwu");
        System.out.println(s);

        System.out.println("打乱顺序");
        Collections.shuffle(str);
        for (String string : str) {
            System.out.println(string+" ");
        }
        System.out.println("填充：");
        Collections.fill(str, "Jolin");
        for (String string : str) {
            System.out.println(string+" "); //内容全部会变成Jolin
        }
    }
}