Can someone tell me what's the problem with my JDK?

You need Java JDK 8 to build for android currently in unity but you have 9.0.4 installed you can uninstall it using Java Uninstall Tool to ensure a clean uninstallation then install Java JDK 8 and build your app again. This way it should work.

Keep in mind that the JDK link I included refers to the 64bit version if you need the 32bit you can get it here