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.

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 the properties of its parent.

Creating Tree in Java

Step 1: Import the necessary package.

In Java it provides 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