JPasswordField and MD5 hashes

Question

I have two methods to make an MD5 String from an entered password in a JPasswordField. Which one is better for security? Can anyone recommend any changes?
* Create MD5 of password field
* @param JPasswordField - location of the password
* @return String - an MD5 hash of the field text
private String getMD5(javax.swing.JPasswordField field) {
    java.security.MessageDigest md;
    String passwdString = "";
    char[] passwdChars = field.getPassword();
    int i;
    field.setText("");
    // char[] to string and blank out chars
    for (i = 0; i < passwdChars.length; i++) {
        passwdString += passwdChars;
passwdChars[i] = 0; // blank after for security
try {
md = java.security.MessageDigest.getInstance("MD5");
} catch (java.security.NoSuchAlgorithmException e) {
return null;
byte[] passwdMD5 = md.digest(passwdString.getBytes());
passwdString = "xxxxxxxxxxxxxxxxxxxxxxxxx"; // security
return dumpBytes(passwdMD5);
* Create MD5 of password field
* @param JPasswordField - location of the password
* @return String - an MD5 hash of the field text
private String getMD5a(javax.swing.JPasswordField field) {
java.security.MessageDigest md;
String MD5;
try {
md = java.security.MessageDigest.getInstance("MD5");
} catch (java.security.NoSuchAlgorithmException e) {
return null;
MD5 = dumpBytes(md.digest(new String(field.getPassword()).getBytes()));
field.setText("");
return MD5;
* Byte[] to String conversion
* @param byte[]
* @return String
private static String dumpBytes(byte[] bytes) {
int i;
StringBuffer sb = new StringBuffer();
for (i=0; i<bytes.length; i++) {
if (i%32 == 0 && i!=0) {
sb.append("\n");
String s = Integer.toHexString(bytes[i]);
if (s.length() < 2) {
s = "0"+s;
if (s.length() > 2) {
s = s.substring(s.length()-2);
sb.append(s);
return sb.toString();

Answer 1

Thanks for the replies.
Unfortunately I can't get the charsToBytes function to work. For example, if you run the following code you can see that it doesn't seem to give me the correct md5 (if you to to http://pajhome.org.uk/crypt/md5/ and calculate the MD5 for 'test' you will see that function getMD5a works but not getMD5b):
public class test {
    public static void main(String args[]) {
        new test();
    public test() {
        char[] chars = {'t','e','s','t'};
        System.out.println("Method a: "+getMD5a(chars));
        System.out.println("Method b: "+getMD5b(chars));
    private String getMD5a(char[] passwd) {
        java.security.MessageDigest md;
        String MD5;
        try {
            md = java.security.MessageDigest.getInstance("MD5");
        } catch (java.security.NoSuchAlgorithmException e) {
            return null;
        MD5 = dumpBytes(md.digest(new String(passwd).getBytes()));
        return MD5;
    private String getMD5b(char[] passwd) {
        java.security.MessageDigest md;
        String MD5;
        try {
            md = java.security.MessageDigest.getInstance("MD5");
        } catch (java.security.NoSuchAlgorithmException e) {
            return null;
        MD5 = dumpBytes(md.digest(charsToBytes(passwd)));
        return MD5;
    public static byte[] charsToBytes(char[] chars) {
        byte[] bytes = new byte[chars.length*2];
        int b,c;
        for (b = 0, c = 0; c < chars.length; c++, b+=2) {
            bytes[b] = (byte)((chars[c] >> 8) & 0xFF);
            bytes[b+1] = (byte)(chars[c] & 0xFF);
        return bytes;
    public static String dumpBytes(byte[] bytes) {
        int i;
        StringBuffer sb = new StringBuffer();
        for (i=0; i<bytes.length; i++) {
            if (i%32 == 0 && i!=0) {
                sb.append("\n");
            String s = Integer.toHexString(bytes);
if (s.length() < 2) {
s = "0"+s;
if (s.length() > 2) {
s = s.substring(s.length()-2);
sb.append(s);
return sb.toString();