import java.io.StringWriter;
 
public class HexHelper
{
  /**
   * Convert an int to a hexadecimal string.
   */
  public static String toString(int i) {
    StringBuffer sb = new StringBuffer();
    for(int p=0; p<8; p++) {
      byte b = (byte)(i & 0xf);
      sb.append(nibbleToDigit(b));
      i >>= 4;
    }
 
    return sb.toString();
  }
 
  /** 
   * Converts the lower four bits of a byte into the ascii digit 
   * which represents its hex value. For example:
   * nibbleToDigit(10) produces 'a'.
   */
  public static char nibbleToDigit(byte x) {
    char c = (char)(x & 0xf); // mask low nibble
    return(c > 9 ? (char)(c - 10 + 'a') : (char)(c + '0')); // int to hex char
  }
 
  /**
   * Convert a single byte into a string representing its hex value.
   * i.e. -1 -> "ff"
   * @param b the byte to convert.
   * @return a string containing the hex equivalent.
   */
  public static String toString(byte b) {
    StringBuffer sb = new StringBuffer();
    sb.append(nibbleToDigit((byte)(b >> 4)));
    sb.append(nibbleToDigit(b));
    return sb.toString();
  }
 
  /**
   * Returns a text representation of a byte array.
   *
   * @param bytes a byte array
   * @return a string containing the hex equivalent of the bytes.
   */
  public static String toString(byte [] bytes) {
    StringWriter sw = new StringWriter();
 
    int length = bytes.length;
    if(length > 0) {
      for(int i = 0; i < length; i++) {
        sw.write(toString(bytes[i]));
        if(i != length - 1)
          sw.write(" ");
      }
    }
    return(sw.toString());
  }
}

String hexString = HexHelper.toString( unicodeString.getBytes() );