I have been working as an Android developer for the past 1.8 years and recently left my job. Even though I have decent knowledge of Android development, I believe one can never rely only on one technology. 

Hence, I am now taking an online course in Java with data structures from a reputed institute, because I have never been good with data structures and algorithms. I have decided that for the next 3-4 months, I will concentrate only on improving my skills through this course and not take up a job. 

After completing this course, how should I explain this gap in my resume?