import javax.xml.bind.DatatypeConverter;
import java.io.UnsupportedEncodingException;
public class test {
    public static void main(String[] args) throws UnsupportedEncodingException{
         //print hex string version of HELLO WORLD
        byte[] helloBytes = "HELLO WORLD".getBytes();
        String helloHex = DatatypeConverter.printHexBinary(helloBytes);
        System.out.printf("Hello hex: 0x%s\n", helloHex);
 
        //convert hex-encoded string back to original string
        byte[] decodedHex = DatatypeConverter.parseHexBinary(helloHex);
        String decodedString = new String(decodedHex, "UTF-8");
        System.out.printf("Hello decoded : %s\n", decodedString);    
    }
}

final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
public static String bytesToHex(byte[] bytes) {
    char[] hexChars = new char[bytes.length * 2];
    for ( int j = 0; j < bytes.length; j++ ) {
        int v = bytes[j] & 0xFF;
        hexChars[j * 2] = hexArray[v >>> 4];
        hexChars[j * 2 + 1] = hexArray[v & 0x0F];
    }
    return new String(hexChars);
}

private static final char[] hexCode = "0123456789ABCDEF".toCharArray();

    public String printHexBinary(byte[] data) {
        StringBuilder r = new StringBuilder(data.length * 2);
        for (byte b : data) {
            r.append(hexCode[(b >> 4) & 0xF]);
            r.append(hexCode[(b & 0xF)]);
        }
        return r.toString();
    }