SelfFlatProfilePrinter.java:

package org.jruby.runtime.profile.builtin;
// because: MethodData is not public in org.jruby.runtime.profile.builtin; cannot be accessed from outside package

import org.jruby.runtime.profile.builtin.ProfilePrinter;
import org.jruby.runtime.profile.builtin.ProfileData;
import org.jruby.runtime.profile.builtin.Invocation;
import org.jruby.runtime.profile.builtin.MethodData;

(copy of FlatProfilePrinter)
public class SelfFlatProfilePrinter extends ProfilePrinter {
  // ...
}

Java::JavaLang::IllegalAccessError: tried to access class org.jruby.runtime.profile.builtin.MethodData from class org.jruby.runtime.profile.builtin.SelfFlatProfilePrinter
from java.lang.reflect.Method.invoke(java/lang/reflect/Method.java:606)

Java::JavaLang::IllegalAccessError: org/jruby/runtime/profile/builtin/MethodData
from java.lang.reflect.Method.invoke(java/lang/reflect/Method.java:606)