JAVA) What kind of function does a simple addition also have to go through in Kernel???

The operating system is in charge of managing the entire computer The part that the normal process, not the operating system, can resolve using commands from the CPU can behave independently of the kernel.

Most modern kernels are available only when time-sharing processing (multis-threading) or parts related to device access (all inputs/outputs and device controls) enter the kernel. In addition, the memory that the process must use can only be managed by the kernel. Functions related to these functions enter and return to the kernel on request in the normal process (user process), which is called System Call.

The API uses a system call if necessary, so unless you are developing a system-related tool, such as a device driver or a file system, it is sufficient to program only the API provided.

If you're going to make the bottom first, you have to learn the kernel.

If you're just going to make the current application, Google will support it with API, so you can use it.

You don't have to study the kernel to make an application right now