When a junior developer joins our team, it is interesting to realize how mastering language syntax and API is just a small part of the skills that matter.
Just after the syntax and API knowledge (actually knowing where to find what you want in the API is enough), there are a few other skills you definitely must know.
First is unit test. It is not difficult to begin with that, it is not that easy to tune tests so that they dont depend on too many things, to save time when refactoring. Also mocking objects is the next step.
Mastering dependencies is another key to successful software development. Dependency Injection is a buzzword for a very simple idea, that everyone can apply only by being aware to do the ”new” where is it most convenient to change, using valued constructors or setters.
Design patterns are of course an essential tool to build flexible software. Everytime there is a design problem, design and analysis patterns often provide a good solution. They also guide you to good object-oriented thinking. However, when there is no design problem, there is no need for patterns.
The last very important thing to understand in software development is to look for simplicity, always. It is easy to build a complicated solution, it is difficult to build a simple one. But a simple solution has so many advantages… To simplify a design, domain analysis is a great tool; the more you understand the domain, the best you can align your design to it, and the simplest it will be. By separating orthogonal things or by unifying similar things you can also simplify.
There are also things that we must unlearn, like doing design first and testing at the very end of a project; it is most of the time also useless to create extensive UML diagrams, good design can hardly come from diagrams, if you are not close enough to the code you may miss the point and have a flawed design, even though it looks great as a diagram.
It is counter-intuitive to beginners to focus on anything but syntax. Therefore, unless you have a colleague to introduce you to other concerns, or unless you are really motivated to look for advises on the Internet, you can live a long time without even knowing there is more than that…