I am getting what look like the same error when I run the SDK Manager from inside B4A.
I downloaded the Command Line tools from
https://dl.google.com/android/repository/sdk-tools-windows-4333796.zip as in the page Erel suggested and I still get the same error.
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.sun.xml.bind.v2.runtime.reflect.opt.Injector$1 (file:/E:/Development/Androidnew/tools/bin/jaxb-impl-2.1.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int)
WARNING: Please consider reporting this to the maintainers of com.sun.xml.bind.v2.runtime.reflect.opt.Injector$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
B4a Version 10.0
SDK Manager 3.62
Open JDK 11.0.1