Working With Tree in Java

Introduction

This article describes working with a Tree structure in Java. The Tree is a very common component and I think all of you have seen them in many applications. A control that displays a set of hierarchical data as an outline. You can find task-oriented documentation and examples of using trees in Ebooks content.
A specific node in a tree can be identified either by a TreePath (an object that encapsulates a node and all of its ancestors), or by its display row, where each row in the display area displays one node. An expanded node is a non-leaf node (as identified by TreeModel.isLeaf(node) returning false) that will display its children when all its ancestors are expanded. A collapsed node is one which hides them. A hidden node is one which is under a collapsed ancestor. All of a viewable nodes parents are expanded, but may or may not be displayed. A displayed node is both viewable and in the display area, where it can be seen.  

Following are components Descriptions of the tree.

JTree : The tree is a graphical representation of data with the hierarchical properties by adding nodes to nodes and keeps the relation as parent and child.

Node : A node is an object and is available at any position within the JTree where the data associated is represented.
 
Path : The path is a collection of a contiguous set of nodes that contains one or many nodes. The path is empty or null when the path does not have a node.

Leaf : This is a special type of node at the end of a path. A leaf node is not connected to other nodes.

Root : This is the node at the highest point within the hierarchy in a tree.
 
Parent :  It represents the relationship of node with another node. In object-oriented programming concepts the parent is a super class.

Child : It represents the relationship of node with another node. In object-oriented programming concepts the child is a subclass of its parent. It inherits all properties of its parent.

For Creating the Tree you have to use the following steps.

Step 1 : Import the necessary package.

In Java it provide a spate package with in swing named as tree.
import javax.swing.*;
import javax.swing.tree.*;

Step 2 : Create the DefaultMutableTreeNode objects as required.

DefaultMutableTreeNode c = new DefaultMutableTreeNode("Collage", true);

DefaultMutableTreeNode d = new DefaultMutableTreeNode("Department");

DefaultMutableTreeNode f = new DefaultMutableTreeNode("Faculty");

DefaultMutableTreeNode a = new DefaultMutableTreeNode("Acoountant");

DefaultMutableTreeNode r = new DefaultMutableTreeNode("Resgistrar");

DefaultMutableTreeNode m = new DefaultMutableTreeNode("Managenent");

DefaultMutableTreeNode s = new DefaultMutableTreeNode("Security");

Step 3 : Now add all the nodes according your requirements for making a parent-child relation.

c.add(d);

d.add(f);

d.add(a);

d.add(m);

m.add(s );

c.add(a);

Step 4 : Create an object of the JTree class by passing the parent node (c) in JTree.

JTree mytree = new JTree(c);
 

Step 5 : At last you create a frame and add the tree into the frame.

JFrame frame = new JFrame("Demo of JTree Component!");

frame.add(mytree);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.setUndecorated(true);

frame.getRootPane().setWindowDecorationStyle(JRootPane.PLAIN_DIALOG);

frame.setSize(450,450);

frame.setVisible(true);

Step 6 : Now you can combine the code and run your Jtree Demo program.

Complete code

import javax.swing.*;

import javax.swing.tree.*;

public class TreeComponent

{

public static void main(String[] args)

{

DefaultMutableTreeNode c = new DefaultMutableTreeNode("Collage", true);

DefaultMutableTreeNode d = new DefaultMutableTreeNode("Department");

DefaultMutableTreeNode f = new DefaultMutableTreeNode("Faculty");

DefaultMutableTreeNode a = new DefaultMutableTreeNode("Acoountant");

DefaultMutableTreeNode r = new DefaultMutableTreeNode("Resgistrar");

DefaultMutableTreeNode m = new DefaultMutableTreeNode("Managenent");

DefaultMutableTreeNode s = new DefaultMutableTreeNode("Security");

c.add(d);

d.add(f);

d.add(a);

d.add(m);

m.add(s );

c.add(a);

JTree mytree = new JTree(c);

JFrame frame = new JFrame("Demo of JTree Component!");

frame.add(mytree);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.setUndecorated(true);

frame.getRootPane().setWindowDecorationStyle(JRootPane.PLAIN_DIALOG);

frame.setSize(450,450);

frame.setVisible(true);

}

}

Output:

cmd output

Initial output

After Expanding the tree

Resources

Describing the Java Packages
Use of ByteStreams and CharacterStreams in JAVA
Garbage Collector in .NET
Describing the JSF Elements