https://openjdk.java.net/ 
public interface com.sun.org.apache.bcel.internal.generic.ClassObserver
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: com.sun.org.apache.bcel.internal.generic.ClassObserver
  super_class: java.lang.Object
{
  public abstract void notify(com.sun.org.apache.bcel.internal.generic.ClassGen);
    descriptor: (Lcom/sun/org/apache/bcel/internal/generic/ClassGen;)V
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    MethodParameters:
       Name  Flags
      clazz  
}
SourceFile: "ClassObserver.java"