install_java.md - put version and package requirement in non-platform specific section at top of page

[jsbiff]

I totally understand why you don't put Linux install instructions, since there are a dozen popular Linux distros with different installation methods, and several dozen less popular distros.

But, to figure out that I should install Java 25 and the JDK package for my distro,I had to expand the "Windows" section.

I would recommend, that since the major version is not platform specific, that information should be moved out of the Windows platform specific section. Also, maybe add a brief explanation of the difference between the jdk package (dev tools + jre) and the jre package (runtime to run java apps, but no tools), and instructions that regardless of which platform you are using, you should install the Java 25 JDK package.

[Zabuzard]

Worth noting that the JDK/JRE split has become obsolete somewhere around Java 8-10. Developers are supposed to download a JDK. Users are supposed to not download anything but the app they want to use. Developers are supposed to bundle a custom-made JRE with their apps by using the tools jlink and/or jpackage. Especially this means that users do not have to worry about JDK/JRE anymore, they just download the app they want to use and it is standalone.

Long story short, I dont think that the book should explain JDK versus JRE. Or, its at least not important to know anymore.