import java.security.MessageDigest;

String content = "xxx";

MessageDigest digest = MessageDigest.getInstance("MD5");

digest.update(content.getBytes());

byte[] messageDigest = digest.digest();

vars.put("RESULT",toHexString(messageDigest));

 public String toHexString(byte[] b) {

    char[] HEX_DIGITS = ['0', '1', '2', '3', '4', '5','6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];

    StringBuilder sb = new StringBuilder(b.length * 2);

    for (int i = 0; i < b.length; i++) {

        sb.append(HEX_DIGITS[(b[i] & 0xf0) >>> 4]);

        sb.append(HEX_DIGITS[b[i] & 0x0f]);

    }

    return sb.toString();

}