code: public static byte[] str2bytes(String str) throws IOException {
  		byte[] b=new byte[str.length()];
  		for(int i=0; i<str.length(); ++i) {
  			char c=str.charAt(i);	
  			if(c>255) throw new UnsupportedEncodingException("string contained a char > 255, cannot convert to bytes");
  			b[i]=(byte)c;
  		}
  		return b;
  	}
docs: Convert a string to a byte array, no encoding is used. String must only contain characters <256.