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. 
abstract class com.google.common.collect.Sets$ImprovedAbstractSet<E> extends java.util.AbstractSet<E>
  minor version: 0
  major version: 59
  flags: flags: (0x0420) ACC_SUPER, ACC_ABSTRACT
  this_class: com.google.common.collect.Sets$ImprovedAbstractSet
  super_class: java.util.AbstractSet
{
  void <init>();
    descriptor: ()V
    flags: (0x0000) 
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.google.common.collect.Sets$ImprovedAbstractSet this
         0: .line 77
            aload 0 /* this */
            invokespecial java.util.AbstractSet.<init>:()V
            return
        end local 0 // com.google.common.collect.Sets$ImprovedAbstractSet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/collect/Sets$ImprovedAbstractSet<TE;>;

  public boolean removeAll(java.util.Collection<?>);
    descriptor: (Ljava/util/Collection;)Z
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // com.google.common.collect.Sets$ImprovedAbstractSet this
        start local 1 // java.util.Collection c
         0: .line 80
            aload 0 /* this */
            aload 1 /* c */
            invokestatic com.google.common.collect.Sets.removeAllImpl:(Ljava/util/Set;Ljava/util/Collection;)Z
            ireturn
        end local 1 // java.util.Collection c
        end local 0 // com.google.common.collect.Sets$ImprovedAbstractSet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/collect/Sets$ImprovedAbstractSet<TE;>;
            0    1     1     c  Ljava/util/Collection<*>;
    Signature: (Ljava/util/Collection<*>;)Z
    MethodParameters:
      Name  Flags
      c     

  public boolean retainAll(java.util.Collection<?>);
    descriptor: (Ljava/util/Collection;)Z
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // com.google.common.collect.Sets$ImprovedAbstractSet this
        start local 1 // java.util.Collection c
         0: .line 85
            aload 0 /* this */
            aload 1 /* c */
            invokestatic com.google.common.base.Preconditions.checkNotNull:(Ljava/lang/Object;)Ljava/lang/Object;
            checkcast java.util.Collection
            invokespecial java.util.AbstractSet.retainAll:(Ljava/util/Collection;)Z
            ireturn
        end local 1 // java.util.Collection c
        end local 0 // com.google.common.collect.Sets$ImprovedAbstractSet this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/collect/Sets$ImprovedAbstractSet<TE;>;
            0    1     1     c  Ljava/util/Collection<*>;
    Signature: (Ljava/util/Collection<*>;)Z
    MethodParameters:
      Name  Flags
      c     
}
Signature: <E:Ljava/lang/Object;>Ljava/util/AbstractSet<TE;>;
SourceFile: "Sets.java"
NestHost: com.google.common.collect.Sets
InnerClasses:
  abstract ImprovedAbstractSet = com.google.common.collect.Sets$ImprovedAbstractSet of com.google.common.collect.Sets