public class GetImgSize {public static void main(String[] args) {String posUrl = "http://file11info.ppdai.com/4e598e3bd163405d90d8f7b7783d494d.jpg";byte[] a = getBy(posUrl);System.out.println(a.length);}private static byte[] getBy(String posUrl){try {URL url = new URL(posUrl);ByteArrayOutputStream outputStream = new ByteArrayOutputStream();try(InputStream inputStream = url.openStream()){int len = 0;byte[] buffer = new byte[1024];while (-1 != (len = inputStream.read(buffer))){outputStream.write(buffer, 0, len);}}return outputStream.toByteArray();} catch (Exception e) {e.printStackTrace();}return null;}
}

public class GetImgSize {public static void main(String[] args) throws IOException {String posUrl = "http://file11info.ppdai.com/4e598e3bd163405d90d8f7b7783d494d.jpg";byte[] a = compress(posUrl);System.out.println(a.length);File output = new File("./duke-compressed-005.jpg");OutputStream out = null;try {out = new FileOutputStream(output);out.write(a);} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally {if(out != null){out.flush();out.close();}}}

private static byte[] compress(String posUrl) throws IOException {    ByteArrayOutputStream bos = new ByteArrayOutputStream();    ImageOutputStream ios = null;    byte [] data = null;    ImageWriter writer = null;    try {        URL url = new URL(posUrl);        BufferedImage bufferedImage = ImageIO.read(url);

        writer = ImageIO.getImageWritersByFormatName("jpg").next();

        ios = ImageIO.createImageOutputStream(bos);

        writer.setOutput(ios);

        ImageWriteParam param = writer.getDefaultWriteParam();        if (param.canWriteCompressed()){            param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);            param.setCompressionQuality(0.5f);        }

        writer.write(null, new IIOImage(bufferedImage, null, null), param);

        data = bos.toByteArray();

        return data;    } catch (Exception e) {        e.printStackTrace();    }finally {        bos.close();

        if(ios != null){            ios.close();        }

        if(writer != null){            writer.dispose();        }    }    return null;}

 }