filename extension

 1 import java.util.Scanner;
 2 /**
 3  * 
 4  * Please create a function to extract the filename extension from the given path, return the extracted filename extension or null if none.
 5  *     1、用"/" 分割取最后一项
 6  *  2、用"." 分割取最后一项
 7  */
 8 public class Main {
 9     public static void main(String[] args) {
10         Scanner sc = new Scanner(System.in);
11         String s = sc.nextLine();
12         String[] ss = s.split("/");
13          s = ss[ss.length-1];
14         String[]s1=s.split("\\."); // .是转义字符 不能直接编写
15         if (s1.length>1) {
16             s = s1[s1.length-1];
17         }else {
18             s=null;
19         }    
20         System.out.println(s);
21     }
22 }