Technical requirements
To code in Java or run Java programs on your desktop, you need a computer and operating system that supports the Java Development Kit (JDK). There are JDKs available for different operating systems and different central processing units (CPUs). If you are running the Windows operating system, your only concern is whether you are running 32-bit or 64-bit. On macOS, there are versions of Java for both Intel and Apple (ARM) CPUs. If your operating system is Linux, there are more variations depending on your computer’s hardware. There is even a version of Java for IBM mainframes that run Linux.
The only other hardware requirement is the amount of RAM on your system. I have run Java applications on a Raspberry Pi 3 Model B with just 1 GB of RAM. As a developer, you are doing more than just running programs. You run editors, compilers, web servers, database servers, and your usual software. Doing this needs memory. I recommend a minimum of 8 GB for a development system; 16 GB is ideal, and 32 GB might let you play games while you code.