XMLSlideShow sourcePresentation = new XMLSlideShow(new FileInputStream("data/input/" + inFileName + ".pptx"));
Dimension dim = sourcePresentation.getPageSize();
List<XSLFSlide> slides = sourcePresentation.getSlides();

int id = 0;
for(XSLFSlide slide : slides) {
    XMLSlideShow targetPresentation = new XMLSlideShow();
    targetPresentation.setPageSize(dim);
    targetPresentation.createSlide(slide.getSlideLayout()).importContent(slide);
    targetPresentation.write(new FileOutputStream(outDir + "/" + inFileName + "_slide_" + id + ".pptx"));
    targetPresentation.close();
    id++;
}
sourcePresentation.close();