去哪儿笔试：filename extension

去哪儿笔试：filename extension

题目描述

Please create a function to extract the filename extension from the given path,return the extracted filename extension or null if none.
输入描述:
输入数据为一个文件路径
输出描述:
对于每个测试实例，要求输出对应的filename extension
示例1
输入

Abc/file.txt
输出

txt

思路：

考查字符串的常用方法

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()) {
            String line = sc.nextLine();
            int index = line.lastIndexOf('.') + 1;
            String result = (index == 0) ? "null" : line.substring(index);
            System.out.println(result);
        }
        sc.close();
    }
}