edu.stanford.nlp.trees.SimpleTree Maven / Gradle / Ivy
package edu.stanford.nlp.trees;
import edu.stanford.nlp.ling.Label;
import java.util.List;
/**
* A SimpleTree is a minimal concrete implementation of an
* unlabeled, unscored Tree. It has a tree structure, but
* nothing is stored at a node (no label or score).
* So, most of the time, this is the wrong class to use!
* Look at {@code LabeledScoredTreeNode}.
*
* @author Christopher Manning
*/
public class SimpleTree extends Tree {
private static final long serialVersionUID = -8075763706877132926L;
/**
* Daughters of the parse tree.
*/
private Tree[] daughterTrees;
/**
* Create an empty parse tree.
*/
public SimpleTree() {
daughterTrees = EMPTY_TREE_ARRAY;
}
/**
* Create parse tree with given root and null daughters.
*
* @param label root label of new tree to construct. For a SimpleTree
* this parameter is ignored.
*/
public SimpleTree(Label label) {
this();
}
/**
* Create parse tree with given root and array of daughter trees.
*
* @param label root label of tree to construct. For a SimpleTree
* this parameter is ignored
* @param daughterTreesList list of daughter trees to construct.
*/
public SimpleTree(Label label, List daughterTreesList) {
setChildren(daughterTreesList);
}
/**
* Returns an array of children for the current node, or null
* if it is a leaf.
*/
@Override
public Tree[] children() {
return daughterTrees;
}
/**
* Sets the children of this Tree. If given
* null, this method sets the Tree's children to a
* unique zero-length Tree[] array.
*
* @param children An array of child trees
*/
@Override
public void setChildren(Tree[] children) {
if (children == null) {
System.err.println("Warning -- you tried to set the children of a SimpleTree to null.\nYou should be really using a zero-length array instead.");
daughterTrees = EMPTY_TREE_ARRAY;
} else {
daughterTrees = children;
}
}
// extra class guarantees correct lazy loading (Bloch p.194)
private static class TreeFactoryHolder {
static final TreeFactory tf = new SimpleTreeFactory();
}
/**
* Return a TreeFactory that produces trees of the
* SimpleTree type.
* The factory returned is always the same one (a singleton).
*
* @return a factory to produce simple (unlabelled) trees
*/
@Override
public TreeFactory treeFactory() {
return TreeFactoryHolder.tf;
}
/**
* Return a TreeFactory that produces trees of the
* SimpleTree type.
* The factory returned is always the same one (a singleton).
*
* @return a factory to produce simple (unlabelled) trees
*/
public static TreeFactory factory() {
return TreeFactoryHolder.tf;
}
}