https://github.com/eclipse/eclipse-collections/eclipse-collections: Eclipse Collections is a collections framework for Java. It has JDK-compatible List, Set and Map implementations with a rich API and set of utility classes that work with any JDK compatible Collections, Arrays, Maps or Strings. The iteration protocol was inspired by the Smalltalk collection framework.
  • Craig P. Motlin
  • Donald Raab
  • Mohammad A. Rezaei
  • Hiroshi Ito
  • Nikhil J. Nanivadekar 
public class org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator extends org.eclipse.collections.impl.map.mutable.UnifiedMap<K, V>.PositionalIterator<K>
  minor version: 0
  major version: 59
  flags: flags: (0x0021) ACC_PUBLIC, ACC_SUPER
  this_class: org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator
  super_class: org.eclipse.collections.impl.map.mutable.UnifiedMap$PositionalIterator
{
  final org.eclipse.collections.impl.map.mutable.UnifiedMap this$0;
    descriptor: Lorg/eclipse/collections/impl/map/mutable/UnifiedMap;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  protected void <init>(org.eclipse.collections.impl.map.mutable.UnifiedMap);
    descriptor: (Lorg/eclipse/collections/impl/map/mutable/UnifiedMap;)V
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator this
         0: .line 2458
            aload 0 /* this */
            aload 1
            putfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.this$0:Lorg/eclipse/collections/impl/map/mutable/UnifiedMap;
            aload 0 /* this */
            aload 1
            invokespecial org.eclipse.collections.impl.map.mutable.UnifiedMap$PositionalIterator.<init>:(Lorg/eclipse/collections/impl/map/mutable/UnifiedMap;)V
            return
        end local 0 // org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/map/mutable/UnifiedMap$KeySetIterator;
    MethodParameters:
        Name  Flags
      this$0  final

  protected K nextFromChain();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=3, locals=3, args_size=1
        start local 0 // org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator this
         0: .line 2462
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.this$0:Lorg/eclipse/collections/impl/map/mutable/UnifiedMap;
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap.table:[Ljava/lang/Object;
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.position:I
            iconst_1
            iadd
            aaload
            checkcast java.lang.Object[]
            astore 1 /* chain */
        start local 1 // java.lang.Object[] chain
         1: .line 2463
            aload 1 /* chain */
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.chainPosition:I
            aaload
            astore 2 /* cur */
        start local 2 // java.lang.Object cur
         2: .line 2464
            aload 0 /* this */
            dup
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.chainPosition:I
            iconst_2
            iadd
            putfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.chainPosition:I
         3: .line 2465
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.chainPosition:I
            aload 1 /* chain */
            arraylength
            if_icmpge 5
         4: .line 2466
            aload 1 /* chain */
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.chainPosition:I
            aaload
            ifnonnull 7
         5: .line 2468
      StackMap locals: java.lang.Object[] java.lang.Object
      StackMap stack:
            aload 0 /* this */
            iconst_0
            putfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.chainPosition:I
         6: .line 2469
            aload 0 /* this */
            dup
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.position:I
            iconst_2
            iadd
            putfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.position:I
         7: .line 2471
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            iconst_1
            putfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.lastReturned:Z
         8: .line 2472
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.this$0:Lorg/eclipse/collections/impl/map/mutable/UnifiedMap;
            aload 2 /* cur */
            invokevirtual org.eclipse.collections.impl.map.mutable.UnifiedMap.nonSentinel:(Ljava/lang/Object;)Ljava/lang/Object;
            areturn
        end local 2 // java.lang.Object cur
        end local 1 // java.lang.Object[] chain
        end local 0 // org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator this
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0    9     0   this  Lorg/eclipse/collections/impl/map/mutable/UnifiedMap$KeySetIterator;
            1    9     1  chain  [Ljava/lang/Object;
            2    9     2    cur  Ljava/lang/Object;
    Signature: ()TK;

  public K next();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=3, args_size=1
        start local 0 // org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator this
         0: .line 2478
            aload 0 /* this */
            invokevirtual org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.hasNext:()Z
            ifne 2
         1: .line 2480
            new java.util.NoSuchElementException
            dup
            ldc "next() called, but the iterator is exhausted"
            invokespecial java.util.NoSuchElementException.<init>:(Ljava/lang/String;)V
            athrow
         2: .line 2482
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            dup
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.count:I
            iconst_1
            iadd
            putfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.count:I
         3: .line 2483
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.this$0:Lorg/eclipse/collections/impl/map/mutable/UnifiedMap;
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap.table:[Ljava/lang/Object;
            astore 1 /* table */
        start local 1 // java.lang.Object[] table
         4: .line 2484
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.chainPosition:I
            ifeq 7
         5: .line 2486
            aload 0 /* this */
            invokevirtual org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.nextFromChain:()Ljava/lang/Object;
            areturn
         6: .line 2490
      StackMap locals: java.lang.Object[]
      StackMap stack:
            aload 0 /* this */
            dup
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.position:I
            iconst_2
            iadd
            putfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.position:I
         7: .line 2488
      StackMap locals:
      StackMap stack:
            aload 1 /* table */
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.position:I
            aaload
            ifnull 6
         8: .line 2492
            aload 1 /* table */
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.position:I
            aaload
            astore 2 /* cur */
        start local 2 // java.lang.Object cur
         9: .line 2493
            aload 2 /* cur */
            getstatic org.eclipse.collections.impl.map.mutable.UnifiedMap.CHAINED_KEY:Ljava/lang/Object;
            if_acmpne 11
        10: .line 2495
            aload 0 /* this */
            invokevirtual org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.nextFromChain:()Ljava/lang/Object;
            areturn
        11: .line 2497
      StackMap locals: java.lang.Object
      StackMap stack:
            aload 0 /* this */
            dup
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.position:I
            iconst_2
            iadd
            putfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.position:I
        12: .line 2498
            aload 0 /* this */
            iconst_1
            putfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.lastReturned:Z
        13: .line 2499
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator.this$0:Lorg/eclipse/collections/impl/map/mutable/UnifiedMap;
            aload 2 /* cur */
            invokevirtual org.eclipse.collections.impl.map.mutable.UnifiedMap.nonSentinel:(Ljava/lang/Object;)Ljava/lang/Object;
            areturn
        end local 2 // java.lang.Object cur
        end local 1 // java.lang.Object[] table
        end local 0 // org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator this
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0   14     0   this  Lorg/eclipse/collections/impl/map/mutable/UnifiedMap$KeySetIterator;
            4   14     1  table  [Ljava/lang/Object;
            9   14     2    cur  Ljava/lang/Object;
    Signature: ()TK;
}
Signature: Lorg/eclipse/collections/impl/map/mutable/UnifiedMap<TK;TV;>.PositionalIterator<TK;>;
SourceFile: "UnifiedMap.java"
NestHost: org.eclipse.collections.impl.map.mutable.UnifiedMap
InnerClasses:
  protected KeySetIterator = org.eclipse.collections.impl.map.mutable.UnifiedMap$KeySetIterator of org.eclipse.collections.impl.map.mutable.UnifiedMap
  protected abstract PositionalIterator = org.eclipse.collections.impl.map.mutable.UnifiedMap$PositionalIterator of org.eclipse.collections.impl.map.mutable.UnifiedMap