https://github.com/google/guava/guava: Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more. 
abstract class com.google.common.collect.ForwardingImmutableSet<E>
  minor version: 0
  major version: 59
  flags: flags: (0x0420) ACC_SUPER, ACC_ABSTRACT
  this_class: com.google.common.collect.ForwardingImmutableSet
  super_class: java.lang.Object
{
  private void <init>();
    descriptor: ()V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.google.common.collect.ForwardingImmutableSet this
         0: .line 28
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // com.google.common.collect.ForwardingImmutableSet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/collect/ForwardingImmutableSet<TE;>;
}
Signature: <E:Ljava/lang/Object;>Ljava/lang/Object;
SourceFile: "ForwardingImmutableSet.java"
    RuntimeInvisibleAnnotations: 
      com.google.common.annotations.GwtCompatible(emulated = true)