1: First, look at your age, where you work, and if you are still young, have the capital to study, and are deep in first-tier cities, then I suggest you study university data, which is the future direction now, and first-tier cities are easy to find jobs, but it takes a long time to learn java well, and it will take 2-3 years if it is fast enough, mainly. I'm still optimistic about java and big data in the future.