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. 
final class com.google.common.collect.TreeTraverser$PostOrderNode<T>
  minor version: 0
  major version: 59
  flags: flags: (0x0030) ACC_FINAL, ACC_SUPER
  this_class: com.google.common.collect.TreeTraverser$PostOrderNode
  super_class: java.lang.Object
{
  final T root;
    descriptor: Ljava/lang/Object;
    flags: (0x0010) ACC_FINAL
    Signature: TT;

  final java.util.Iterator<T> childIterator;
    descriptor: Ljava/util/Iterator;
    flags: (0x0010) ACC_FINAL
    Signature: Ljava/util/Iterator<TT;>;

  void <init>(T, java.util.Iterator<T>);
    descriptor: (Ljava/lang/Object;Ljava/util/Iterator;)V
    flags: (0x0000) 
    Code:
      stack=2, locals=3, args_size=3
        start local 0 // com.google.common.collect.TreeTraverser$PostOrderNode this
        start local 1 // java.lang.Object root
        start local 2 // java.util.Iterator childIterator
         0: .line 209
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 210
            aload 0 /* this */
            aload 1 /* root */
            invokestatic com.google.common.base.Preconditions.checkNotNull:(Ljava/lang/Object;)Ljava/lang/Object;
            putfield com.google.common.collect.TreeTraverser$PostOrderNode.root:Ljava/lang/Object;
         2: .line 211
            aload 0 /* this */
            aload 2 /* childIterator */
            invokestatic com.google.common.base.Preconditions.checkNotNull:(Ljava/lang/Object;)Ljava/lang/Object;
            checkcast java.util.Iterator
            putfield com.google.common.collect.TreeTraverser$PostOrderNode.childIterator:Ljava/util/Iterator;
         3: .line 212
            return
        end local 2 // java.util.Iterator childIterator
        end local 1 // java.lang.Object root
        end local 0 // com.google.common.collect.TreeTraverser$PostOrderNode this
      LocalVariableTable:
        Start  End  Slot           Name  Signature
            0    4     0           this  Lcom/google/common/collect/TreeTraverser$PostOrderNode<TT;>;
            0    4     1           root  TT;
            0    4     2  childIterator  Ljava/util/Iterator<TT;>;
    Signature: (TT;Ljava/util/Iterator<TT;>;)V
    MethodParameters:
               Name  Flags
      root           
      childIterator  
}
Signature: <T:Ljava/lang/Object;>Ljava/lang/Object;
SourceFile: "TreeTraverser.java"
NestHost: com.google.common.collect.TreeTraverser
InnerClasses:
  private final PostOrderNode = com.google.common.collect.TreeTraverser$PostOrderNode of com.google.common.collect.TreeTraverser