Programming tutorial books.

As far as I know, assembly language is the closest to the hardware; besides, everything written in other programs is translated into assembly. Also, to understand the program code itself, you need to know assembly, and it's also called the language of hackers.
It's true that it takes longer, but it's the only way to maximize program optimization.

Maximizing program optimization is necessary if the program runs on weak hardware, such as microcontrollers. On PCs with their multi-core processors and gigahertz frequencies, this is not relevant. Java is generally an interpreted language, and its performance is lower than that of compiled languages like C++, but it has its own tasks and areas of application, within which the language is quite suitable, and there is no need to focus on strict optimization. And assembly is, in general, excessive hardcore; it is enough to know the basic commands and the general structure of the processor to understand what is happening during program execution, and more is not required for a programmer in a high-level language, in my opinion. Assembly may have been the language of "hackers" in the 1990s when malicious programs tried to physically disable the computer, but now the priorities of creators of malicious software are completely different. For example, they want to steal data over the network, for which assembly is completely unsuitable.