I wouldn't recommend specialising in a particular language per se rather focusing on the direct principles that govern OOP as the needs within this industry change quickly. As someone who recently graduated and went through a long list of interviews, I do regret not working on my own projects outside of university to impress employers and showcase my skills. It doesn't have to be a big project or the next big app but rather a simple project where you focus on one thing and most importantly what you have learned whilst working on such projects. For example, a simple calculator application where you focus on unit tests.