private void addButtonListener(JButton b) {
		b.addActionListener(new ActionListener() {

			@Override
			public void actionPerformed(ActionEvent ev) {
				if (ev.getActionCommand().equals("Choose Source Folder")) {
					srcF = fileChooser();
					if (srcF == null) {
						src.setText("no Source Folder selected");
					} else
						src.setText(srcF);

				} else if (ev.getActionCommand().equals(
						"Choose Destination Folder")) {

					desF = fileChooser();
					if (desF == null) {
						des.setText("no Destination Folder selected");
					} else
						des.setText(desF);

				} else if (ev.getActionCommand().equals("Start")) {

					if (srcF == null) {
						println("no source choosed!");
						return;
					} 
					if (desF == null) {
						println("no destination choosed!");
						return;
					}

					ArrayList<File> liste = new ArrayList<File>();
					liste = scanforRDF(srcF);
					if (liste.isEmpty()) {
						println("There are no RDF files in directory");
						return;
					}
					if (liste.size() == 1) {
						println("There is one RDF element.");
					} else
						println("There are " + liste.size() + " RDF elements.");
					println("Started!");
					execution(liste);
					println("finished!");
					info.setText("finished!");

				}

			}
		});
	}