File __pngFile = new File("exportUnit.png");
File __jpgFile = new File("exportUnit.jpg");
writeJPEG(__pngFile, __jpgFile, 80);
 
public static void writeJPEG(File $source, File $dest, int $quality) throws IOException
{
    String __formatName = "jpeg";
    BufferedImage __image = ImageIO.read($source);
    ImageWriter __writer = ImageIO.getImageWritersByFormatName(__formatName).next();
    ImageWriteParam __writeParam = __writer.getDefaultWriteParam();
    FileOutputStream __out = new FileOutputStream($dest);
    __writeParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
    __writeParam.setCompressionQuality((float)$quality/100f);
    __writer.setOutput(ImageIO.createImageOutputStream(__out));
    __writer.write(null, new IIOImage(__image, null, null), __writeParam);
    __out.flush();
    __out.close();
    __writer.dispose();
}