Most popular languages have a version of this, including Java. This is only one level of documentation, and one must know a bit about what they don't know to us

Most popular languages have a version of this, including Java. This is only one level of documentation, and one must know a bit about what they don't know to use it effectively. In other words, if you already know that you need to use the foo function, then the foo function's documentation is great. If you don't even know which function or class/module to use, it isn't a great starting point.