Appknox Software Engineer Java interview questions

First round was to solve the problem statement using java only which they have given in mail The Problem Statement: Let us have a file scanning scenario. Let the file be a general property file, where key value pairs are stored.We have a three different properties file, with different contents. Whenever someone makes change (add/delete/modify property) in the properties file and then saves, the application’s task is to print the property file’s name with old key pair value and new key pair value on the console. Second round was telephonic interview , the interviewer asked questions on DS , core java (Collection framework, Thread , io package,wrapper classes). Third round of interview was scheduled with the CTO of the company ,he scheduled the interview twice but he never taken the interview.He just wasted my time.