https://www.graalvm.org/ 
public interface com.oracle.truffle.sl.test.SLDebugTest$Fac
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: com.oracle.truffle.sl.test.SLDebugTest$Fac
  super_class: java.lang.Object
{
  public abstract long fac(long, com.oracle.truffle.sl.test.SLDebugTest$Multiply);
    descriptor: (JLcom/oracle/truffle/sl/test/SLDebugTest$Multiply;)J
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    RuntimeVisibleAnnotations: 
      org.graalvm.polyglot.HostAccess$Export()
    MethodParameters:
          Name  Flags
      n         
      multiply  
}
SourceFile: "SLDebugTest.java"
NestHost: com.oracle.truffle.sl.test.SLDebugTest
InnerClasses:
  public abstract Fac = com.oracle.truffle.sl.test.SLDebugTest$Fac of com.oracle.truffle.sl.test.SLDebugTest
  public Multiply = com.oracle.truffle.sl.test.SLDebugTest$Multiply of com.oracle.truffle.sl.test.SLDebugTest
  public abstract Export = org.graalvm.polyglot.HostAccess$Export of org.graalvm.polyglot.HostAccess
    RuntimeVisibleAnnotations: 
      java.lang.FunctionalInterface()