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copied!<p>Just as <a href="https://stackoverflow.com/users/491245/phoneixs">PhoenixS</a> has mentioned in his answer above, the procedure involves the following steps:</p> <ol> <li>Read the <code>.txt</code> file line by line. In this example we use <a href="http://docs.oracle.com/javase/6/docs/api/java/io/BufferedReader.html" rel="nofollow noreferrer">BufferedReader</a> in conjunction with <a href="http://docs.oracle.com/javase/1.4.2/docs/api/java/io/InputStreamReader.html" rel="nofollow noreferrer">InputStreamReader</a> OR <a href="http://docs.oracle.com/javase/1.4.2/docs/api/java/io/FileReader.html" rel="nofollow noreferrer">FileReader</a>, depending on whether we are reading the <code>.txt</code> file as a resource or from the File System respectively.</li> <li>Depending on the formatting of the <code>.txt</code> file, use the delimiter to determine the hierarchy level of each line as it is being read. Use this to create the relevant nodes of your <code>Jtree</code>. In this case the <code>.txt</code> file is tab-delimited, with the number of tabs indicating the hierarchy level. </li> </ol> <p>Here is the <code>TreeFromTextFile</code> class I wrote:</p> <pre><code>/* * File: TreeFromTextFile.java * Created 2013-02-06 * This Class creates a JTree using data from a Specially formatted text File. * The supplied text file is tab-delimited, as illustrated at: * https://stackoverflow.com/questions/14724014/create-jtree-using-data-from-text-file * * You can use either InputStreamReader to read thetext file as a resource * or use FileReader to read the text file from the file System */ import java.io.BufferedReader; //import java.io.FileReader; import java.io.InputStreamReader; import java.io.LineNumberReader; import javax.swing.JTree; import javax.swing.tree.DefaultMutableTreeNode; import javax.swing.tree.TreeSelectionModel; /** * @author engineervix * */ public class TreeFromTextFile { private BufferedReader in; private LineNumberReader ln; private String line; //value of a line in the text file private String root; //value to be used for the root Node of our JTree private String filename = "TheTextFile.txt"; private String encoding = "UTF-8"; private DefaultMutableTreeNode top; private JTree tree; public TreeFromTextFile() { getRootNode(); top = new DefaultMutableTreeNode(root); createNodes(top); //Create a tree that allows one selection at a time. tree = new JTree(top); tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION); } //this method reads the file and prints all the lines to standard output //for testing purposes public void readFile() { try { //in = new BufferedReader(new FileReader("Path\\To\\File.txt")); in = new BufferedReader(new InputStreamReader(getClass().getResourceAsStream(filename), encoding)); while ((line = in.readLine()) != null) { System.out.println(line); } in.close(); } catch (Exception e) { e.printStackTrace(); } } //this method reads the first line in the text file and assigns it //to the root variable which will be used for the root node of our JTree private void getRootNode() { try { //in = new BufferedReader(new FileReader("Path\\To\\File.txt")); in = new BufferedReader(new InputStreamReader(getClass().getResourceAsStream(filename), encoding)); ln = new LineNumberReader(in); if (ln.getLineNumber() == 0) { root = ln.readLine(); //System.out.println(root); } in.close(); } catch (Exception e) { e.printStackTrace(); } } /** * this method counts the number of occurrences of a given * <code>char</code> in the Specified * <code>String</code> source: * https://stackoverflow.com/questions/275944/how-do-i-count-the-number-of-occurrences-of-a-char-in-a-string */ private int countOccurrences(String haystack, char needle) { int count = 0; for (int i = 0; i < haystack.length(); i++) { if (haystack.charAt(i) == needle) { count++; } } return count; } //create the Nodes private void createNodes(DefaultMutableTreeNode top) { DefaultMutableTreeNode category = null; // Level 1 in Hierarchy DefaultMutableTreeNode subCategory = null; // Level 2 in Hierarchy DefaultMutableTreeNode leaf = null; // Level 3 in Hierarchy try { //in = new BufferedReader(new FileReader("Path\\To\\File.txt")); in = new BufferedReader(new InputStreamReader(getClass().getResourceAsStream(filename), encoding)); while ((line = in.readLine()) != null) { if (countOccurrences(line, '\t') == 1) { category = new DefaultMutableTreeNode(line); top.add(category); } else if (countOccurrences(line, '\t') == 2) { subCategory = new DefaultMutableTreeNode(line); category.add(subCategory); } else if (countOccurrences(line, '\t') == 3) { leaf = new DefaultMutableTreeNode(line); subCategory.add(leaf); } //continue the else...if - if you have more levels } in.close(); } catch (Exception e) { e.printStackTrace(); } } public JTree getTree() { return tree; } } </code></pre> <p>To test the above, I wrote the <code>TreeFromTextFileDemo</code> class, which is as shown below:</p> <pre><code>/* * Requires TreeFromTextFile.java */ import java.awt.BorderLayout; import java.awt.Container; import javax.swing.JFrame; import javax.swing.JScrollPane; import javax.swing.JTree; /** * @author engineervix */ public class TreeFromTextFileDemo { private static TreeFromTextFile tr = new TreeFromTextFile(); public static void main(String[] args) { JFrame frame = new JFrame("Demo | Creating JTree From File.txt"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); Container content = frame.getContentPane(); JTree t = tr.getTree(); content.add(new JScrollPane(t), BorderLayout.CENTER); frame.setSize(275, 300); frame.setLocationByPlatform(true); frame.setVisible(true); } } </code></pre> <hr> <p>The following screenshot illustrates the output. You can use <a href="http://pastebin.com/40dAucNS" rel="nofollow noreferrer">this file</a> as a sample text file.</p> <p><img src="https://i.stack.imgur.com/F48v8.jpg" alt="output of <code>TreeFromTextFileDemo.java</code>"></p>

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