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 
final class org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet extends java.util.AbstractSet<K>
  minor version: 0
  major version: 59
  flags: flags: (0x0030) ACC_FINAL, ACC_SUPER
  this_class: org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet
  super_class: java.util.AbstractSet
{
  final org.eclipse.collections.impl.map.mutable.ConcurrentHashMap this$0;
    descriptor: Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  private void <init>(org.eclipse.collections.impl.map.mutable.ConcurrentHashMap);
    descriptor: (Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap;)V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
         0: .line 1624
            aload 0 /* this */
            aload 1
            putfield org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet.this$0:Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap;
            aload 0 /* this */
            invokespecial java.util.AbstractSet.<init>:()V
            return
        end local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap$KeySet;
    MethodParameters:
        Name  Flags
      this$0  final

  public java.util.Iterator<K> iterator();
    descriptor: ()Ljava/util/Iterator;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=1, args_size=1
        start local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
         0: .line 1629
            new org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeyIterator
            dup
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet.this$0:Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap;
            invokespecial org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeyIterator.<init>:(Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap;)V
            areturn
        end local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap$KeySet;
    Signature: ()Ljava/util/Iterator<TK;>;

  public int size();
    descriptor: ()I
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
         0: .line 1635
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet.this$0:Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap;
            invokevirtual org.eclipse.collections.impl.map.mutable.ConcurrentHashMap.size:()I
            ireturn
        end local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap$KeySet;

  public boolean contains(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Z
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
        start local 1 // java.lang.Object o
         0: .line 1641
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet.this$0:Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap;
            aload 1 /* o */
            invokevirtual org.eclipse.collections.impl.map.mutable.ConcurrentHashMap.containsKey:(Ljava/lang/Object;)Z
            ireturn
        end local 1 // java.lang.Object o
        end local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap$KeySet;
            0    1     1     o  Ljava/lang/Object;
    MethodParameters:
      Name  Flags
      o     

  public boolean remove(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Z
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
        start local 1 // java.lang.Object o
         0: .line 1647
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet.this$0:Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap;
            aload 1 /* o */
            invokevirtual org.eclipse.collections.impl.map.mutable.ConcurrentHashMap.remove:(Ljava/lang/Object;)Ljava/lang/Object;
            ifnull 1
            iconst_1
            ireturn
      StackMap locals:
      StackMap stack:
         1: iconst_0
            ireturn
        end local 1 // java.lang.Object o
        end local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    2     0  this  Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap$KeySet;
            0    2     1     o  Ljava/lang/Object;
    MethodParameters:
      Name  Flags
      o     

  public void clear();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
         0: .line 1653
            aload 0 /* this */
            getfield org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet.this$0:Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap;
            invokevirtual org.eclipse.collections.impl.map.mutable.ConcurrentHashMap.clear:()V
         1: .line 1654
            return
        end local 0 // org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    2     0  this  Lorg/eclipse/collections/impl/map/mutable/ConcurrentHashMap$KeySet;
}
Signature: Ljava/util/AbstractSet<TK;>;
SourceFile: "ConcurrentHashMap.java"
NestHost: org.eclipse.collections.impl.map.mutable.ConcurrentHashMap
InnerClasses:
  private final KeyIterator = org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeyIterator of org.eclipse.collections.impl.map.mutable.ConcurrentHashMap
  private final KeySet = org.eclipse.collections.impl.map.mutable.ConcurrentHashMap$KeySet of org.eclipse.collections.impl.map.mutable.ConcurrentHashMap