Class TreeTraverser<T>

java.lang.Object
com.google.common.collect.TreeTraverser<T>
@Deprecated @Beta @GwtCompatible public abstract class TreeTraverser<T> extends Object
Deprecated.
Use Traverser instead. All instance methods have their equivalent on the result of Traverser.forTree(tree) where tree implements SuccessorsFunction, which has a similar API as children(T) or can be the same lambda function as passed into using(Function).

This class is scheduled to be removed in October 2019.

Views elements of a type T as nodes in a tree, and provides methods to traverse the trees induced by this traverser.

For example, the tree 


        h
      / | \
     /  e  \
    d       g
   /|\      |
  / | \     f
 a  b  c

can be iterated over in preorder (hdabcegf), postorder (abcdefgh), or breadth-first order (hdegabcf).

Null nodes are strictly forbidden.

Because this is an abstract class, not an interface, you can't use a lambda expression to implement it: 


 // won't work
 TreeTraverser<NodeType> traverser = node -> node.getChildNodes();
Instead, you can pass a lambda expression to the using factory method: 

 TreeTraverser<NodeType> traverser = TreeTraverser.using(node -> node.getChildNodes());
Since:
15.0
Author:
Louis Wasserman

  • Constructor Details

    • TreeTraverser

      public TreeTraverser()
      Deprecated.
      Constructor for use by subclasses.

  • Method Details

    • using

      @Deprecated public static <T> TreeTraverser<T> using(Function<T,? extends Iterable<T>> nodeToChildrenFunction)
      Deprecated.
      Use Traverser.forTree(com.google.common.graph.SuccessorsFunction<N>) instead. If you are using a lambda, these methods have exactly the same signature.
      Returns a tree traverser that uses the given function to navigate from a node to its children. This is useful if the function instance already exists, or so that you can supply a lambda expressions. If those circumstances don't apply, you probably don't need to use this; subclass TreeTraverser and implement its children(T) method directly.
      Since:
      20.0

    • children

      public abstract Iterable<T> children(T root)
      Deprecated.
      Returns the children of the specified node. Must not contain null.

    • preOrderTraversal

      @Deprecated public final FluentIterable<T> preOrderTraversal(T root)
      Deprecated.
      Use Traverser.depthFirstPreOrder(N) instead, which has the same behavior.
      Returns an unmodifiable iterable over the nodes in a tree structure, using pre-order traversal. That is, each node's subtrees are traversed after the node itself is returned.

      No guarantees are made about the behavior of the traversal when nodes change while iteration is in progress or when the iterators generated by children(T) are advanced.

    • postOrderTraversal

      @Deprecated public final FluentIterable<T> postOrderTraversal(T root)
      Deprecated.
      Use Traverser.depthFirstPostOrder(N) instead, which has the same behavior.
      Returns an unmodifiable iterable over the nodes in a tree structure, using post-order traversal. That is, each node's subtrees are traversed before the node itself is returned.

      No guarantees are made about the behavior of the traversal when nodes change while iteration is in progress or when the iterators generated by children(T) are advanced.

    • breadthFirstTraversal

      @Deprecated public final FluentIterable<T> breadthFirstTraversal(T root)
      Deprecated.
      Use Traverser.breadthFirst(N) instead, which has the same behavior.
      Returns an unmodifiable iterable over the nodes in a tree structure, using breadth-first traversal. That is, all the nodes of depth 0 are returned, then depth 1, then 2, and so on.

      No guarantees are made about the behavior of the traversal when nodes change while iteration is in progress or when the iterators generated by children(T) are advanced.