Regex Tester

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Regex Tester Applet

Complex regex patterns can be difficult to get right first time so here's a simple utility that allows you to test your regex pattern against a line of text to see what happens. The result is displayed in two ways:

The line of text is displayed with the matching areas highlighted (the match is shown bold and coloured). The highlight colour alternates between red and yellow with each match so you see adjacent matches.
Each match is listed showing the text that matched and it's index position in the input text.

The demo above shows the RegexTester running in an applet, alternatively you can download the RegexTester Jar to run on your own machine. To run the downloaded RegexTester just double click on the jar.

License

This software is released under the GNU GPLv3 license

Usage

Enter the regex expression into the Regex field. The previous 10 entries are available by clicking on the arrow down button at the right hand side of the field.
Enter the text to search using the Regex expression into the Input field. The previous 10 entries are available by clicking on the arrow down button at the right hand side of the field.
Click on the 'Run Regex' button and the match fields will display the matches if any.

RegexTester

This is the code for the RegexTester class

/*
 * Copyright (c) 2010 keang Ltd. All Rights Reserved.
 */
package uk.co.keang.regex;

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JComboBox;
import javax.swing.JTextField;
import javax.swing.SwingConstants;
import javax.swing.UIManager;
import javax.swing.WindowConstants;
import javax.swing.border.BevelBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;

import uk.co.keang.swingaddons.VariableGridLayout;


/**
 * Allows the input of a regex expression and a test string and then applies the regex
 * to the test string showing the matches that were made
 *
 * @author keang ltd
 * @version 1.2, 14 May 2010
 */
public class RegexTester extends JPanel
{
private static final long serialVersionUID = -1454574421699687991L;
private JComboBox regexCB;
private JComboBox inputCB;
private JLabel matchLbl;
private JTextArea matchTA;
private Document matchTADoc;
private JButton closeBtn;


public RegexTester()
    {
    initPanel();
    }

private void initPanel()
    {
    KeyAdapter edited = new KeyAdapter()
        {
        @Override
        public void keyTyped(KeyEvent e)
            {
            // clear the current match as soon as a key is pressed
            clearMatch();
            }
        };

    ActionListener inputListener = new ActionListener()
        {
        @Override
        public void actionPerformed(ActionEvent e)
            {
            // add the current entry to the list if it isn't already in the list
            JComboBox cb = (JComboBox)e.getSource();
            String text = (String)cb.getSelectedItem();

            if ( text != null && text.length() > 0 )
                {
                DefaultComboBoxModel model = ((DefaultComboBoxModel)cb.getModel());

                if ( model.getIndexOf(text) < 0 )
                    model.insertElementAt(text, 0);

                if ( model.getSize() > 10 )
                    model.removeElementAt(model.getSize()-1);
                }
            }
        };

    setLayout(new BorderLayout(5, 5));
    setBorder(new EmptyBorder(10, 10, 10, 10));

    // create the regex panel
    JPanel p = new JPanel();
    p.setLayout(new VariableGridLayout(0, 2, 5, 5));
    add(p, BorderLayout.CENTER);

    p.add(new JLabel("Regex", SwingConstants.RIGHT));
    regexCB = new JComboBox();
    regexCB.setEditable(true);
    regexCB.addKeyListener(edited);
    regexCB.addActionListener(inputListener);
    Dimension d = regexCB.getPreferredSize();
    d.width = 200;
    regexCB.setPreferredSize(d);
    p.add(regexCB);

    p.add(new JLabel("Input", SwingConstants.RIGHT));
    inputCB = new JComboBox();
    inputCB.setEditable(true);
    inputCB.addKeyListener(edited);
    inputCB.addActionListener(inputListener);
    p.add(inputCB);

    p.add(new JLabel("Matches", SwingConstants.RIGHT));
    matchLbl = new JLabel();
    matchLbl.setBorder(new BevelBorder(BevelBorder.LOWERED));
    matchLbl.setPreferredSize(d);
    p.add(matchLbl);

    p.add(new JLabel(""));
    matchTA = new JTextArea(10, 60);
    matchTADoc = matchTA.getDocument();
    JScrollPane sp = new JScrollPane(matchTA);
    p.add(sp);

    // create the buttons panel
    p = new JPanel();
    p.setBorder(new EmptyBorder(15, 20, 0, 20));

    p.setLayout(new GridLayout(0, 2, 20, 0));
    add(p, BorderLayout.SOUTH);

    JButton matchBtn = new JButton("Run Regex");
    matchBtn.addActionListener(new ActionListener()
        {
        @Override
        public void actionPerformed(ActionEvent e)
            {
            // run the regex pattern match

            clearMatch();

            // validate the input
            String regexStr = (String)regexCB.getSelectedItem();

            if ( regexStr.length() == 0 )
                {
                JOptionPane.showMessageDialog(RegexTester.this,
                    "The REGEX expression must contain at least 1 character",
                    "No REGEX", JOptionPane.ERROR_MESSAGE);
                return;
                }

            String inputStr = (String)inputCB.getSelectedItem();

            if ( inputStr == null || inputStr.length() == 0 )
                {
                JOptionPane.showMessageDialog(RegexTester.this,
                    "The input text must contain at least 1 character",
                    "No Input", JOptionPane.ERROR_MESSAGE);
                return;
                }

            matchPattern(regexStr, inputStr);
            }
        });

    p.add(matchBtn);

    closeBtn = new JButton("Close");
    closeBtn.addActionListener(new ActionListener()
        {
        @Override
        public void actionPerformed(ActionEvent e)
            {
            // Close the application
            clearMatch();

            Container top = RegexTester.this.getTopLevelAncestor();

            if ( top instanceof Window )
                {
                top.setVisible(false);
                ((Window)top).dispose();
                }
            }
        });
    p.add(closeBtn);
    }

/**
 * Clears the match text areas
 */
private void clearMatch()
    {
    matchLbl.setText("");
    try
        {
        matchTADoc.remove(0, matchTADoc.getLength());
        }
    catch(BadLocationException e1)
        {
        e1.printStackTrace();
        }
    }


/**
 * Matches the pattern
 *
 * @param regexStr the regex
 * @param inputStr the string to match
 */
private void matchPattern(String regexStr, String inputStr)
    {
    Pattern pattern;
    try
        {
        pattern = Pattern.compile(regexStr);
        }
    catch(Exception e)
        {
        matchLbl.setText("<html><font color='red'>Error in REGEX expression</font></html>");
        matchTA.append(e.getMessage());
        return;
        }

    Matcher matcher = pattern.matcher(inputStr);

    StringBuffer sb = new StringBuffer();
    sb.append("<html> ");

    System.out.println("\nLooking for '"+regexStr+"' in '"+inputStr+"'");

    boolean found = false;
    boolean evenMatch = true;
    int i = 0;
    while( matcher.find() )
        {
        int start = matcher.start();
        int end = matcher.end();

        if ( start > i )
            {
            // add the unmatched text
            sb.append("<font color='black'>");
            sb.append(inputStr.substring(i, start));
            sb.append("</font>");
            }

        // add the matched text
        if ( evenMatch )
            sb.append("<font color='red'><b>");
        else
            sb.append("<font color='yellow'><b>");
        sb.append(inputStr.substring(start, end));
        sb.append("</b></font>");

        String str = "\""+matcher.group()+"\" found from " +
                        "index "+matcher.start()+" to "+matcher.end();

        matchTA.append(str);
        matchTA.append("\n");
        System.out.println(str);

        i = end;
        evenMatch = !evenMatch;
        found = true;
        }

    if ( found )
        {
        if ( i < inputStr.length() )
            {
            // add the remaining unmatched text
            sb.append("<font color='black'>");
            sb.append(inputStr.substring(i, inputStr.length()));
            sb.append("</font>");
            }
        }
    else
        {
        sb.append("No matches found");
        }

    sb.append("</html>");

    matchLbl.setText(sb.toString());
    }

/**
 * Sets the text to display on the close button
 *
 * @param text the text to display
 */
public void setCloseButtonText(String text) { closeBtn.setText(text); }

/**
 * Starts the application in a JFrame
 * @param args
 */
public static void main(String[] args)
    {
    try
        {
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }
    catch ( Exception e )
        {
        System.out.println("Failed to set Look and Feel.\n"+e);
        }

    JFrame frame = new JFrame("Regex Tester");
    frame.add(new RegexTester());
    frame.pack();

    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    Dimension d = frame.getSize();
    d.width += 10;
    d.height += 10;
    frame.setSize(d);
    frame.setLocation((screenSize.width-d.width)/2, (screenSize.height-d.height)/2);

    frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
    frame.setVisible(true);
    }
}