I am trying to convert ppt into pdf using Apache POI but getting following error.Please help me out of this - apache-poi

Question

Following code is used:
public static void main(String[] args) throws IOException {
FileInputStream is = new FileInputStream("C:/Users/hp/Downloads/sampPPT.ppt");
HSLFSlideShow ppt = new HSLFSlideShow(is);
is.close();
Dimension pgsize = ppt.getPageSize();
int idx = 1;
for (HSLFSlide slide : ppt.getSlides()) {
BufferedImage img = new BufferedImage(pgsize.width, pgsize.height, BufferedImage.TYPE_INT_RGB);
Graphics2D graphics = img.createGraphics();
// clear the drawing area
graphics.setPaint(Color.white);
graphics.fill(new Rectangle2D.Float(0, 0, pgsize.width, pgsize.height));
// render
slide.draw(graphics);
// save the output
FileOutputStream out = new FileOutputStream("C:/Users/hp/Downloads/slide-" + idx + ".png");
javax.imageio.ImageIO.write(img, "png", out);
out.close();
idx++;
}
}
This throws following exception:
Exception in thread "main" java.lang.IllegalAccessError: class org.apache.poi.hslf.usermodel.HSLFSlideShowImpl tried to access private field org.apache.poi.POIDocument.directory (org.apache.poi.hslf.usermodel.HSLFSlideShowImpl and org.apache.poi.POIDocument are in unnamed module of loader 'app')
at org.apache.poi.hslf.usermodel.HSLFSlideShowImpl.readCurrentUserStream(HSLFSlideShowImpl.java:340)
at org.apache.poi.hslf.usermodel.HSLFSlideShowImpl.<init>(HSLFSlideShowImpl.java:154)
at org.apache.poi.hslf.usermodel.HSLFSlideShowImpl.<init>(HSLFSlideShowImpl.java:127)
at org.apache.poi.hslf.usermodel.HSLFSlideShowImpl.<init>(HSLFSlideShowImpl.java:116)
at org.apache.poi.hslf.usermodel.HSLFSlideShow.<init>(HSLFSlideShow.java:138)
at PPTConv.PPTConv.main(PPTConv.java:27)

Answer 1

To make an answer why such exceptions occur. Maybe it is helpful for others too:
This kind of exception occur if you mix Apache POI jars from different versions. This is not supported. See FAQ.
In that special case there probably are poi-*.jar and poi-scratchpad-*.jar from different versions in classpath. The class org.apache.poi.hslf.usermodel.HSLFSlideShowImpl, which extends org.apache.poi.POIDocument, is contained in poi-scratchpad-*.jar while org.apache.poi.POIDocument is contained in poi-*.jar. If those *.jars are from different versions, then following can occur:
The org.apache.poi.hslf.usermodel.HSLFSlideShowImpl of poi-scratchpad-3.15.jar calls currentUser = new CurrentUserAtom(directory); in code line 340. This is possible because it extends org.apache.poi.POIDocument and this has field protected DirectoryNode directory; in version 3.15 (poi-3.15.jar).
But the same class org.apache.poi.POIDocument of version 3.16 (poi-3.16.jar) has field private DirectoryNode directory;. So if org.apache.poi.hslf.usermodel.HSLFSlideShowImpl of version 3.15 calls currentUser = new CurrentUserAtom(directory); in code line 340, but org.apache.poi.POIDocument is from version 3.16, then java.lang.IllegalAccessError: class org.apache.poi.hslf.usermodel.HSLFSlideShowImpl tried to access private field org.apache.poi.POIDocument.directory is thrown because it really tries to access a private field now.