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.Sets$5$1 extends com.google.common.collect.AbstractIterator<java.util.Set<E>>
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: com.google.common.collect.Sets$5$1
  super_class: com.google.common.collect.AbstractIterator
{
  final java.util.BitSet bits;
    descriptor: Ljava/util/BitSet;
    flags: (0x0010) ACC_FINAL

  final com.google.common.collect.Sets$5 this$1;
    descriptor: Lcom/google/common/collect/Sets$5;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  private final int val$size;
    descriptor: I
    flags: (0x1012) ACC_PRIVATE, ACC_FINAL, ACC_SYNTHETIC

  private final com.google.common.collect.ImmutableMap val$index;
    descriptor: Lcom/google/common/collect/ImmutableMap;
    flags: (0x1012) ACC_PRIVATE, ACC_FINAL, ACC_SYNTHETIC

  void <init>(com.google.common.collect.Sets$5, com.google.common.collect.ImmutableMap, int);
    descriptor: (Lcom/google/common/collect/Sets$5;Lcom/google/common/collect/ImmutableMap;I)V
    flags: (0x0000) 
    Code:
      stack=4, locals=4, args_size=4
        start local 0 // com.google.common.collect.Sets$5$1 this
         0: .line 1647
            aload 0 /* this */
            aload 1
            putfield com.google.common.collect.Sets$5$1.this$1:Lcom/google/common/collect/Sets$5;
            aload 0 /* this */
            aload 2
            putfield com.google.common.collect.Sets$5$1.val$index:Lcom/google/common/collect/ImmutableMap;
            aload 0 /* this */
            iload 3
            putfield com.google.common.collect.Sets$5$1.val$size:I
            aload 0 /* this */
            invokespecial com.google.common.collect.AbstractIterator.<init>:()V
         1: .line 1648
            aload 0 /* this */
            new java.util.BitSet
            dup
            aload 2
            invokevirtual com.google.common.collect.ImmutableMap.size:()I
            invokespecial java.util.BitSet.<init>:(I)V
            putfield com.google.common.collect.Sets$5$1.bits:Ljava/util/BitSet;
         2: .line 1647
            return
        end local 0 // com.google.common.collect.Sets$5$1 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    3     0  this  Lcom/google/common/collect/Sets$5$1;
    MethodParameters:
           Name  Flags
      this$0     final
      val$index  final
      val$size   final

  protected java.util.Set<E> computeNext();
    descriptor: ()Ljava/util/Set;
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=6, locals=3, args_size=1
        start local 0 // com.google.common.collect.Sets$5$1 this
         0: .line 1652
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.bits:Ljava/util/BitSet;
            invokevirtual java.util.BitSet.isEmpty:()Z
            ifeq 3
         1: .line 1653
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.bits:Ljava/util/BitSet;
            iconst_0
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.val$size:I
            invokevirtual java.util.BitSet.set:(II)V
         2: .line 1654
            goto 10
         3: .line 1655
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.bits:Ljava/util/BitSet;
            iconst_0
            invokevirtual java.util.BitSet.nextSetBit:(I)I
            istore 1 /* firstSetBit */
        start local 1 // int firstSetBit
         4: .line 1656
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.bits:Ljava/util/BitSet;
            iload 1 /* firstSetBit */
            invokevirtual java.util.BitSet.nextClearBit:(I)I
            istore 2 /* bitToFlip */
        start local 2 // int bitToFlip
         5: .line 1658
            iload 2 /* bitToFlip */
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.val$index:Lcom/google/common/collect/ImmutableMap;
            invokevirtual com.google.common.collect.ImmutableMap.size:()I
            if_icmpne 7
         6: .line 1659
            aload 0 /* this */
            invokevirtual com.google.common.collect.Sets$5$1.endOfData:()Ljava/lang/Object;
            checkcast java.util.Set
            areturn
         7: .line 1675
      StackMap locals: int int
      StackMap stack:
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.bits:Ljava/util/BitSet;
            iconst_0
            iload 2 /* bitToFlip */
            iload 1 /* firstSetBit */
            isub
            iconst_1
            isub
            invokevirtual java.util.BitSet.set:(II)V
         8: .line 1676
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.bits:Ljava/util/BitSet;
            iload 2 /* bitToFlip */
            iload 1 /* firstSetBit */
            isub
            iconst_1
            isub
            iload 2 /* bitToFlip */
            invokevirtual java.util.BitSet.clear:(II)V
         9: .line 1677
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.bits:Ljava/util/BitSet;
            iload 2 /* bitToFlip */
            invokevirtual java.util.BitSet.set:(I)V
        end local 2 // int bitToFlip
        end local 1 // int firstSetBit
        10: .line 1679
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.bits:Ljava/util/BitSet;
            invokevirtual java.util.BitSet.clone:()Ljava/lang/Object;
            checkcast java.util.BitSet
            astore 1 /* copy */
        start local 1 // java.util.BitSet copy
        11: .line 1680
            new com.google.common.collect.Sets$5$1$1
            dup
            aload 0 /* this */
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.val$index:Lcom/google/common/collect/ImmutableMap;
            aload 1 /* copy */
            aload 0 /* this */
            getfield com.google.common.collect.Sets$5$1.val$size:I
            invokespecial com.google.common.collect.Sets$5$1$1.<init>:(Lcom/google/common/collect/Sets$5$1;Lcom/google/common/collect/ImmutableMap;Ljava/util/BitSet;I)V
            areturn
        end local 1 // java.util.BitSet copy
        end local 0 // com.google.common.collect.Sets$5$1 this
      LocalVariableTable:
        Start  End  Slot         Name  Signature
            0   12     0         this  Lcom/google/common/collect/Sets$5$1;
            4   10     1  firstSetBit  I
            5   10     2    bitToFlip  I
           11   12     1         copy  Ljava/util/BitSet;
    Signature: ()Ljava/util/Set<TE;>;

  protected java.lang.Object computeNext();
    descriptor: ()Ljava/lang/Object;
    flags: (0x1044) ACC_PROTECTED, ACC_BRIDGE, ACC_SYNTHETIC
    Code:
      stack=1, locals=1, args_size=1
         0: .line 1
            aload 0
            invokevirtual com.google.common.collect.Sets$5$1.computeNext:()Ljava/util/Set;
            areturn
      LocalVariableTable:
        Start  End  Slot  Name  Signature
}
Signature: Lcom/google/common/collect/AbstractIterator<Ljava/util/Set<TE;>;>;
SourceFile: "Sets.java"
EnclosingMethod: com.google.common.collect.Sets$5.iterator:()Ljava/util/Iterator;
NestHost: com.google.common.collect.Sets
InnerClasses:
  com.google.common.collect.Sets$5
  com.google.common.collect.Sets$5$1
  com.google.common.collect.Sets$5$1$1