https://openjdk.java.net/ 
public interface sun.jvm.hotspot.utilities.HeapProgressThunk
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: sun.jvm.hotspot.utilities.HeapProgressThunk
  super_class: java.lang.Object
{
  public abstract void heapIterationFractionUpdate(double);
    descriptor: (D)V
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    MethodParameters:
                       Name  Flags
      fractionOfHeapVisited  

  public abstract void heapIterationComplete();
    descriptor: ()V
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
}
SourceFile: "HeapProgressThunk.java"