I see two paths for finding the desired API:
- open the "Installed JREs" preference page and ask the plug-in spy (Alt-Shift-F1) for the implementing classes. This will let you inspect how the UI access the set of installed JREs
- browse the code starting from class JavaRuntime (inside plug-in org.eclipse.jdt.launching), it should have references to all relevant API:
The central access point for launching support. This class manages the registered VM types contributed through the <code>"org.eclipse.jdt.launching.vmType"</code> extension point..