https://lucene.apache.org/lucene-parent/lucene-core: Apache Lucene Java Core (The Apache Software Foundation) 
public interface org.apache.lucene.search.CollectorManager<C extends org.apache.lucene.search.Collector, T>
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: org.apache.lucene.search.CollectorManager
  super_class: java.lang.Object
{
  public abstract C newCollector();
    descriptor: ()Lorg/apache/lucene/search/Collector;
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    Exceptions:
      throws java.io.IOException
    Signature: ()TC;

  public abstract T reduce(java.util.Collection<C>);
    descriptor: (Ljava/util/Collection;)Ljava/lang/Object;
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    Exceptions:
      throws java.io.IOException
    Signature: (Ljava/util/Collection<TC;>;)TT;
    MethodParameters:
            Name  Flags
      collectors  
}
Signature: <C::Lorg/apache/lucene/search/Collector;T:Ljava/lang/Object;>Ljava/lang/Object;
SourceFile: "CollectorManager.java"