Compute SHA-1 of byte array

What about:

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Formatter;

public static String SHAsum(byte[] convertme) throws NoSuchAlgorithmException{
    MessageDigest md = MessageDigest.getInstance("SHA-1"); 
    return byteArray2Hex(md.digest(convertme));
}

private static String byteArray2Hex(final byte[] hash) {
    Formatter formatter = new Formatter();
    for (byte b : hash) {
        formatter.format("%02x", b);
    }
    return formatter.toString();
}

You can do it yourself but I would recommend to use a library that has been proven to work, like Commons Codec. The class DigestUtils has several methods to calculate hashes.

From CommonCodec DigestUtils Implementation the Hex coversion after the Digest calculation as shown before :

MessageDigest md = MessageDigest.getInstance("SHA-1"); 
return byteArray2Hex(md.digest(convertme));

should be http://commons.apache.org/codec/apidocs/src-html/org/apache/commons/codec/binary/Hex.html#line.129 :

private static final char[] DIGITS_LOWER = 
   {'0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};

private static final char[] DIGITS_UPPER = 
   {'0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

protected static char[] encodeHex(byte[] data, char[] toDigits) {
    int l = data.length;
    char[] out = new char[l << 1];
    // two characters form the hex value.
    for (int i = 0, j = 0; i < l; i++) {
        out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
        out[j++] = toDigits[0x0F & data[i]];
    }
    return out;
}

protected static int toDigit(char ch, int index) throws DecoderException {
    int digit = Character.digit(ch, 16);
    if (digit == -1) {
        throw new DecoderException(
                    "Illegal hexadecimal character " 
            + ch + " at index " + index);
    }
    return digit;
}

public static String exampleSha1(String convertme){
    MessageDigest md = MessageDigest.getInstance("SHA-1"); 
    byte[] encodeHex = md.digest(convertme));
    return new String(encodeHex);
}

This a snippet of code we use to convert to SHA-1 but takes a String instead of a Byte[] see this javadoc for further info

        import java.io.UnsupportedEncodingException;
        import java.security.MessageDigest;
        import java.security.NoSuchAlgorithmException;

        public class DoSHA1 {

            private static String convToHex(byte[] data) {
                StringBuilder buf = new StringBuilder();
                for (int i = 0; i < data.length; i++) {
                    int halfbyte = (data[i] >>> 4) & 0x0F;
                    int two_halfs = 0;
                    do {
                        if ((0 <= halfbyte) && (halfbyte <= 9))
                            buf.append((char) ('0' + halfbyte));
                        else
                            buf.append((char) ('a' + (halfbyte - 10)));
                        halfbyte = data[i] & 0x0F;
                    } while(two_halfs++ < 1);
                }
                return buf.toString();
            }

            public static String SHA1(String text) throws NoSuchAlgorithmException,
UnsupportedEncodingException  {
            MessageDigest md = MessageDigest.getInstance("SHA-1");
            byte[] sha1hash = new byte[40];
            md.update(text.getBytes("iso-8859-1"), 0, text.length());
            sha1hash = md.digest();
            return convToHex(sha1hash);
            }
        }