js和java中使用join来进行数组元素的连接

var arr = new Array(3)
arr[0] = "a"
arr[1] = "b"
arr[2] = "c"

arr.join(".")
a.b.c
------------------
arr.join(",")
a,b,c

        List<String> list = new ArrayList<>();
        list.add("a");
        list.add("b");
        list.add("c");
        String join = String.join("-",list);
        System.out.println(join);

        String[] s = new String[]{"a","b"};
        String join2 = String.join("-",s);
        System.out.println(join2);

       a-b-c
       a-b