Shows how to use Zxing to write/read QR codes

QrCodec.java

import java.awt.image.BufferedImage;
import java.io.File;
import java.util.Base64;
import java.util.Random;

import javax.imageio.ImageIO;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.LuminanceSource;
import com.google.zxing.MultiFormatReader;
import com.google.zxing.Result;
import com.google.zxing.client.j2se.BufferedImageLuminanceSource;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.HybridBinarizer;
import com.google.zxing.qrcode.QRCodeWriter;

public class QrCodec {

	public static void main(String[] args) throws Exception {
		Random random = new Random();
		byte[] data = new byte[(int) (1024*1.5)]; 
		random.nextBytes(data); 
	    String stringData = Base64.getEncoder().encodeToString(data);
        QRCodeWriter qrCodeWriter = new QRCodeWriter();
        BitMatrix bitMatrix = qrCodeWriter.encode(stringData, BarcodeFormat.QR_CODE, 370, 370);

	    File file = new File("qr.png");
        MatrixToImageWriter.writeToPath(bitMatrix, "PNG", file.toPath());
        
        //--- Reading ---
        BufferedImage bufferedImage = ImageIO.read(file);
        LuminanceSource source = new BufferedImageLuminanceSource(bufferedImage);
        BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));

        Result result = new MultiFormatReader().decode(bitmap);
        System.out.println(result.getText());
        System.out.println(result.getText().equals(stringData));
        
	    
	}
}