How to implement a tree data-structure in Java?
Here:
public class Tree<T> { private Node<T> root; public Tree(T rootData) { root = new Node<T>(); root.data = rootData; root.children = new ArrayList<Node<T>>(); } public static class Node<T> { private T data; private Node<T> parent; private List<Node<T>> children; }}That is a basic tree structure that can be used for String or any other object. It is fairly easy to implement simple trees to do what you need.
All you need to add are methods for add to, removing from, traversing, and constructors. The Node is the basic building block of the Tree.
Yet another tree structure:
public class TreeNode<T> implements Iterable<TreeNode<T>> { T data; TreeNode<T> parent; List<TreeNode<T>> children; public TreeNode(T data) { this.data = data; this.children = new LinkedList<TreeNode<T>>(); } public TreeNode<T> addChild(T child) { TreeNode<T> childNode = new TreeNode<T>(child); childNode.parent = this; this.children.add(childNode); return childNode; } // other features ...}Sample usage:
TreeNode<String> root = new TreeNode<String>("root");{ TreeNode<String> node0 = root.addChild("node0"); TreeNode<String> node1 = root.addChild("node1"); TreeNode<String> node2 = root.addChild("node2"); { TreeNode<String> node20 = node2.addChild(null); TreeNode<String> node21 = node2.addChild("node21"); { TreeNode<String> node210 = node20.addChild("node210"); } }}BONUS
See fully-fledged tree with:
- iterator
- searching
- Java/C#
There is actually a pretty good tree structure implemented in the JDK.
Have a look at javax.swing.tree, TreeModel, and TreeNode. They are designed to be used with the JTreePanel but they are, in fact, a pretty good tree implementation and there is nothing stopping you from using it with out a swing interface.
Note that as of Java 9 you may wish not to use these classes as they will not be present in the 'Compact profiles'.