import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.WriterException;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

import java.util.HashMap;
import java.util.Map;
//.......
private BitMatrix createBitMatrix(String qrCodeText, int size) throws WriterException {
  Map<EncodeHintType, Object> hints = new HashMap<>();
  hints.put(EncodeHintType.MARGIN, DEFAULT_MARGIN);
  hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.H);
  return new QRCodeWriter().encode(qrCodeText, BarcodeFormat.QR_CODE, size, size, hints);
}