Regular expression checker

Question

hi,
i am new to regular expression. i would like to know if there is a tool to check regular expressions? the tool should based on the entered regular expression display the result.
thanks

Answer 1

import java.util.regex.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class JavaRegxTest extends JFrame implements ActionListener{
  JTextField regxInput, textInput;
  JButton doMatchButton, resetButton, exitButton;
  JTextArea resultsArea;
  public JavaRegxTest(){
    super("JavaRegxTest");
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    Container cp = getContentPane();
    cp.setLayout(new GridLayout(2, 1));
    JPanel upPanel = new JPanel(new GridLayout(5, 1));
    upPanel.add(new JLabel("regular expression:   "));
    upPanel.add(regxInput = new JTextField(50));
    upPanel.add(new JLabel("sample text:          "));
    upPanel.add(textInput = new JTextField(50));
    JPanel buttonPanel = new JPanel(new GridLayout(1, 3));
    buttonPanel.add(resetButton = new JButton("RESET"));
    buttonPanel.add(doMatchButton = new JButton("MATCH"));
    buttonPanel.add(exitButton = new JButton("EXIT"));
    upPanel.add(buttonPanel);
    resetButton.addActionListener(this);
    doMatchButton.addActionListener(this);
    exitButton.addActionListener(this);
    resultsArea = new JTextArea(20, 60);
    resultsArea.setEditable(false);
    JScrollPane jsp = new JScrollPane(resultsArea);
    cp.add(upPanel);
    cp.add(jsp);
    setSize(550, 700);
    setVisible(true);
  public void actionPerformed(ActionEvent e){
    JButton btn = (JButton)(e.getSource());
    if (btn == exitButton){
      System.exit(0);
    else if (btn == resetButton){
      reset();
    else if (btn == doMatchButton){
      doMatch();
  /* clear text */
  void reset(){
    regxInput.setText("");
    textInput.setText("");
    resultsArea.setText("");
  /* display match results */
  void doMatch(){
    resultsArea.setText(resultsArea.getText() + "REGX=" + regxInput.getText()
     + "\n" + "TEXT=" + textInput.getText() + "\n");
    try{
      Pattern pat = Pattern.compile(regxInput.getText());
      String sampleText = textInput.getText();
      Matcher mat = pat.matcher(sampleText);
      int gc = mat.groupCount();
      for (int i = 0; i <= gc; ++i){ //for each capture group
        resultsArea.setText(resultsArea.getText()
         + "GROUP" + i + " : \n"); //GROUP0 == whole match
        while (mat.find()){ //display every matched parts
          resultsArea.setText(resultsArea.getText()
           + " " + mat.group(i) + "\n");
        mat.reset(sampleText); //go to next group
    catch(Exception e){
      resultsArea.setText(e.toString());
  public static void main(String[] args){
    JavaRegxTest jrt = new JavaRegxTest();
}