Java/Security/General

Message Digest Test

import java.awt.Container;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import javax.swing.ButtonGroup;
import javax.swing.JCheckBox;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
public class MessageDigestTest {
  public static void main(String[] args) {
    JFrame f = new MessageDigestFrame();
    f.show();
  }
}
class MessageDigestFrame extends JFrame {
  public MessageDigestFrame() {
    setTitle("MessageDigestTest");
    setSize(400, 200);
    addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
    JPanel panel = new JPanel();
    ButtonGroup group = new ButtonGroup();
    ActionListener listener = new ActionListener() {
      public void actionPerformed(ActionEvent event) {
        JCheckBox b = (JCheckBox) event.getSource();
        setAlgorithm(b.getText());
      }
    };
    addCheckBox(panel, "SHA-1", group, true, listener);
    addCheckBox(panel, "MD5", group, false, listener);
    Container contentPane = getContentPane();
    contentPane.add(panel, "North");
    contentPane.add(new JScrollPane(message), "Center");
    contentPane.add(digest, "South");
    digest.setFont(new Font("Monospaced", Font.PLAIN, 12));
    setAlgorithm("SHA-1");
    JMenuBar menuBar = new JMenuBar();
    JMenu menu = new JMenu("File");
    JMenuItem fileDigestItem = new JMenuItem("File digest");
    fileDigestItem.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent event) {
        loadFile();
      }
    });
    menu.add(fileDigestItem);
    JMenuItem textDigestItem = new JMenuItem("Text area digest");
    textDigestItem.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent event) {
        String m = message.getText();
        computeDigest(m.getBytes());
      }
    });
    menu.add(textDigestItem);
    menuBar.add(menu);
    setJMenuBar(menuBar);
  }
  public void addCheckBox(Container c, String name, ButtonGroup g,
      boolean selected, ActionListener listener) {
    JCheckBox b = new JCheckBox(name, selected);
    c.add(b);
    g.add(b);
    b.addActionListener(listener);
  }
  public void setAlgorithm(String alg) {
    try {
      currentAlgorithm = MessageDigest.getInstance(alg);
      digest.setText("");
    } catch (NoSuchAlgorithmException e) {
      digest.setText("" + e);
    }
  }
  public void loadFile() {
    JFileChooser chooser = new JFileChooser();
    chooser.setCurrentDirectory(new File("."));
    int r = chooser.showOpenDialog(this);
    if (r == JFileChooser.APPROVE_OPTION) {
      String name = chooser.getSelectedFile().getAbsolutePath();
      computeDigest(loadBytes(name));
    }
  }
  public byte[] loadBytes(String name) {
    FileInputStream in = null;
    try {
      in = new FileInputStream(name);
      ByteArrayOutputStream buffer = new ByteArrayOutputStream();
      int ch;
      while ((ch = in.read()) != -1)
        buffer.write(ch);
      return buffer.toByteArray();
    } catch (IOException e) {
      if (in != null) {
        try {
          in.close();
        } catch (IOException e2) {
        }
      }
      return null;
    }
  }
  public void computeDigest(byte[] b) {
    currentAlgorithm.reset();
    currentAlgorithm.update(b);
    byte[] hash = currentAlgorithm.digest();
    String d = "";
    for (int i = 0; i < hash.length; i++) {
      int v = hash[i] & 0xFF;
      if (v < 16)
        d += "0";
      d += Integer.toString(v, 16).toUpperCase() + " ";
    }
    digest.setText(d);
  }
  private JTextArea message = new JTextArea();
  private JTextField digest = new JTextField();
  private MessageDigest currentAlgorithm;
}