如何在不提供其他源代码的情况下共享Java功能？

When programming in C++ we have header files and source files. When our company sells our product (which is just a library of useful functions essentially) we provide the client only our header files and compiled source code (not the actual source code). This way clients buying the code see the function definitions in the header files and can make calls to these functions using the compiled code. When programming in C++ we have header files an