2018 Xiao Hong Book School Recruit Software Research and development on-line written test program second question __ programming

Title: Given a string s and integral type number k, you need to flip the first k characters in the 2k character. Flips all characters when the remaining characters are less than k characters, and when the remaining characters are greater than or equal to K characters and less than 2k characters, the first k characters are flipped and the remaining characters remain the same. The characters contain only English lowercase letters, which are no more than 10000 in length.
Input Description: string s and integer number K
Output Description: The flipped string.
Example:
Input: abc,2
Output: CBA
Input: abcdef,2
Output: Bacdef
The method I use is substring () and reverse () in StringBuffer.
All the code is as follows:




Please, everyone passing by Daniel.