Every Java developer wants to improve their programming skills. You may be great at Java but not quite excellent at problem-solving skills. Today's age is comprised of language experts than true developers. Although it is easy to comprehend java programming language keywords, processes, and APIs, It's difficult to solve practical challenges, develop reusable and optimized applications, and get the most out of the algorithm and data structure.
To be a better Java developer, you have to be quite good at the algorithm, data structure, multi-threading, developing using OOP, and different developing concepts such as divide and conquer , recursion, unit testing, ...