Class TreeTraverser<T>
- java.lang.Object
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- com.google.common.collect.TreeTraverser<T>
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- Direct Known Subclasses:
BinaryTreeTraverser
@Beta @GwtCompatible public abstract class TreeTraverser<T> extends java.lang.Object
Views elements of a typeT
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.
For Java 8 users: Because this is an abstract class, not an interface, you can't use a lambda expression to extend it:
Instead, you can pass a lambda expression to the// won't work TreeTraverser<NodeType> traverser = node -> node.getChildNodes();
using
factory method:TreeTraverser<NodeType> traverser = TreeTraverser.using(node -> node.getChildNodes());
- Since:
- 15.0
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Constructor Summary
Constructors Constructor Description TreeTraverser()
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description FluentIterable<T>
breadthFirstTraversal(T root)
Returns an unmodifiable iterable over the nodes in a tree structure, using breadth-first traversal.abstract java.lang.Iterable<T>
children(T root)
Returns the children of the specified node.FluentIterable<T>
postOrderTraversal(T root)
Returns an unmodifiable iterable over the nodes in a tree structure, using post-order traversal.FluentIterable<T>
preOrderTraversal(T root)
Returns an unmodifiable iterable over the nodes in a tree structure, using pre-order traversal.static <T> TreeTraverser<T>
using(Function<T,? extends java.lang.Iterable<T>> nodeToChildrenFunction)
Returns a tree traverser that uses the given function to navigate from a node to its children.
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Method Detail
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using
public static <T> TreeTraverser<T> using(Function<T,? extends java.lang.Iterable<T>> nodeToChildrenFunction)
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; subclassTreeTraverser
and implement itschildren(T)
method directly.- Since:
- 20.0
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children
public abstract java.lang.Iterable<T> children(T root)
Returns the children of the specified node. Must not contain null.
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preOrderTraversal
public final FluentIterable<T> preOrderTraversal(T root)
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.
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postOrderTraversal
public final FluentIterable<T> postOrderTraversal(T root)
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.
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breadthFirstTraversal
public final FluentIterable<T> breadthFirstTraversal(T root)
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.
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