用java实现生成二维码

要用Java实现生成二维码，你可以使用ZXing库。下面是一个简单的示例代码：

import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.imageio.ImageIO;

public class QRCodeGenerator {

    public static void main(String[] args) {
        String text = "Hello, world!";
        int width = 300;
        int height = 300;
        String format = "png";
        String filePath = "qrcode.png";

        Map<EncodeHintType, Object> hints = new HashMap<>();
        hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");

        try {
            BitMatrix bitMatrix = new MultiFormatWriter().encode(text, BarcodeFormat.QR_CODE, width, height, hints);

            BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
            for (int x = 0; x < width; x++) {
                for (int y = 0; y < height; y++) {
                    image.setRGB(x, y, bitMatrix.get(x, y) ? 0xFF000000 : 0xFFFFFFFF);
                }
            }

            ImageIO.write(image, format, new File(filePath));
            System.out.println("QR Code generated successfully!");

        } catch (Exception e) {
            System.err.println("Failed to generate QR Code: " + e.getMessage());
        }
    }
}