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.Multimaps$Keys$1$1 extends com.google.common.collect.Multisets$AbstractEntry<K>
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: com.google.common.collect.Multimaps$Keys$1$1
  super_class: com.google.common.collect.Multisets$AbstractEntry
{
  final com.google.common.collect.Multimaps$Keys$1 this$2;
    descriptor: Lcom/google/common/collect/Multimaps$Keys$1;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  private final java.util.Map$Entry val$backingEntry;
    descriptor: Ljava/util/Map$Entry;
    flags: (0x1012) ACC_PRIVATE, ACC_FINAL, ACC_SYNTHETIC

  void <init>(com.google.common.collect.Multimaps$Keys$1, java.util.Map$Entry);
    descriptor: (Lcom/google/common/collect/Multimaps$Keys$1;Ljava/util/Map$Entry;)V
    flags: (0x0000) 
    Code:
      stack=2, locals=3, args_size=3
        start local 0 // com.google.common.collect.Multimaps$Keys$1$1 this
         0: .line 1703
            aload 0 /* this */
            aload 1
            putfield com.google.common.collect.Multimaps$Keys$1$1.this$2:Lcom/google/common/collect/Multimaps$Keys$1;
            aload 0 /* this */
            aload 2
            putfield com.google.common.collect.Multimaps$Keys$1$1.val$backingEntry:Ljava/util/Map$Entry;
            aload 0 /* this */
            invokespecial com.google.common.collect.Multisets$AbstractEntry.<init>:()V
            return
        end local 0 // com.google.common.collect.Multimaps$Keys$1$1 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/collect/Multimaps$Keys$1$1;
    MethodParameters:
                  Name  Flags
      this$0            final
      val$backingEntry  final

  public K getElement();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.google.common.collect.Multimaps$Keys$1$1 this
         0: .line 1706
            aload 0 /* this */
            getfield com.google.common.collect.Multimaps$Keys$1$1.val$backingEntry:Ljava/util/Map$Entry;
            invokeinterface java.util.Map$Entry.getKey:()Ljava/lang/Object;
            areturn
        end local 0 // com.google.common.collect.Multimaps$Keys$1$1 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/collect/Multimaps$Keys$1$1;
    Signature: ()TK;

  public int getCount();
    descriptor: ()I
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.google.common.collect.Multimaps$Keys$1$1 this
         0: .line 1711
            aload 0 /* this */
            getfield com.google.common.collect.Multimaps$Keys$1$1.val$backingEntry:Ljava/util/Map$Entry;
            invokeinterface java.util.Map$Entry.getValue:()Ljava/lang/Object;
            checkcast java.util.Collection
            invokeinterface java.util.Collection.size:()I
            ireturn
        end local 0 // com.google.common.collect.Multimaps$Keys$1$1 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/collect/Multimaps$Keys$1$1;
}
Signature: Lcom/google/common/collect/Multisets$AbstractEntry<TK;>;
SourceFile: "Multimaps.java"
EnclosingMethod: com.google.common.collect.Multimaps$Keys$1.transform:(Ljava/util/Map$Entry;)Lcom/google/common/collect/Multiset$Entry;
NestHost: com.google.common.collect.Multimaps
InnerClasses:
  Keys = com.google.common.collect.Multimaps$Keys of com.google.common.collect.Multimaps
  com.google.common.collect.Multimaps$Keys$1
  com.google.common.collect.Multimaps$Keys$1$1
  public abstract Entry = com.google.common.collect.Multiset$Entry of com.google.common.collect.Multiset
  abstract AbstractEntry = com.google.common.collect.Multisets$AbstractEntry of com.google.common.collect.Multisets
  public abstract Entry = java.util.Map$Entry of java.util.Map