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. 
class com.google.common.collect.ImmutableEnumSet$EnumSerializedForm<E extends java.lang.Enum<E>> implements java.io.Serializable
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: com.google.common.collect.ImmutableEnumSet$EnumSerializedForm
  super_class: java.lang.Object
{
  final java.util.EnumSet<E> delegate;
    descriptor: Ljava/util/EnumSet;
    flags: (0x0010) ACC_FINAL
    Signature: Ljava/util/EnumSet<TE;>;

  private static final long serialVersionUID;
    descriptor: J
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL
    ConstantValue: 0

  void <init>(java.util.EnumSet<E>);
    descriptor: (Ljava/util/EnumSet;)V
    flags: (0x0000) 
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // com.google.common.collect.ImmutableEnumSet$EnumSerializedForm this
        start local 1 // java.util.EnumSet delegate
         0: .line 145
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 146
            aload 0 /* this */
            aload 1 /* delegate */
            putfield com.google.common.collect.ImmutableEnumSet$EnumSerializedForm.delegate:Ljava/util/EnumSet;
         2: .line 147
            return
        end local 1 // java.util.EnumSet delegate
        end local 0 // com.google.common.collect.ImmutableEnumSet$EnumSerializedForm this
      LocalVariableTable:
        Start  End  Slot      Name  Signature
            0    3     0      this  Lcom/google/common/collect/ImmutableEnumSet$EnumSerializedForm<TE;>;
            0    3     1  delegate  Ljava/util/EnumSet<TE;>;
    Signature: (Ljava/util/EnumSet<TE;>;)V
    MethodParameters:
          Name  Flags
      delegate  

  java.lang.Object readResolve();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0000) 
    Code:
      stack=3, locals=1, args_size=1
        start local 0 // com.google.common.collect.ImmutableEnumSet$EnumSerializedForm this
         0: .line 151
            new com.google.common.collect.ImmutableEnumSet
            dup
            aload 0 /* this */
            getfield com.google.common.collect.ImmutableEnumSet$EnumSerializedForm.delegate:Ljava/util/EnumSet;
            invokevirtual java.util.EnumSet.clone:()Ljava/util/EnumSet;
            invokespecial com.google.common.collect.ImmutableEnumSet.<init>:(Ljava/util/EnumSet;)V
            areturn
        end local 0 // com.google.common.collect.ImmutableEnumSet$EnumSerializedForm this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/collect/ImmutableEnumSet$EnumSerializedForm<TE;>;
}
Signature: <E:Ljava/lang/Enum<TE;>;>Ljava/lang/Object;Ljava/io/Serializable;
SourceFile: "ImmutableEnumSet.java"
NestHost: com.google.common.collect.ImmutableEnumSet
InnerClasses:
  private EnumSerializedForm = com.google.common.collect.ImmutableEnumSet$EnumSerializedForm of com.google.common.collect.ImmutableEnumSet