Java is one of the most popular programming languages. More than 2 billion devices run under Java
One can not write efficient code without the proper idea of algorithms. None of algorithms work for all problems. So, one should be wise choosing algorithm to solve the given problem.
Any fool can write code that a computer can understand. Good programmers write code that humans can understand.-Martin Fowler
There are some popular design patterns which we can use in plug and play manner or we can say that they are there to be copy and pasted. The knowledge of design patterns saves our time and also our code adheres to the standard practices. In other word, no need to reinvent the wheel.
Design patterns are powerful, and it's easy to see all kinds of ways they can be used in your current designs. Developers naturally love to create beautiful architectures that are ready to take on change from all directions.- Head First Design Patterns
Linux is written in C and if you want to find out implementation detail about operation system, linux would be the best choice.
“C++ is designed to allow you to express ideas, but if you don't have ideas or don't have any clue about how to express them, C++ doesn't offer much help.”
― Bjarne Stroustrup