https://lucene.apache.org/lucene-parent/lucene-core: Apache Lucene Java Core (The Apache Software Foundation) 
interface org.apache.lucene.index.IndexWriter$Event
  minor version: 0
  major version: 59
  flags: flags: (0x0600) ACC_INTERFACE, ACC_ABSTRACT
  this_class: org.apache.lucene.index.IndexWriter$Event
  super_class: java.lang.Object
{
  public abstract void process(org.apache.lucene.index.IndexWriter);
    descriptor: (Lorg/apache/lucene/index/IndexWriter;)V
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    Exceptions:
      throws java.io.IOException
    MethodParameters:
        Name  Flags
      writer  
}
SourceFile: "IndexWriter.java"
NestHost: org.apache.lucene.index.IndexWriter
InnerClasses:
  abstract Event = org.apache.lucene.index.IndexWriter$Event of org.apache.lucene.index.IndexWriter
    RuntimeVisibleAnnotations: 
      java.lang.FunctionalInterface()