public GraphtoDLConverter () {
		JFileChooser fileChooser = new JFileChooser(".");
        int ret = fileChooser.showOpenDialog(null);
        if (ret != JFileChooser.APPROVE_OPTION) {
        	System.err.println("User cancelation.");
        	return;
        }
        
        if (!loadGraph(fileChooser.getSelectedFile())) {
        	System.err.println("Failed to load graph file: " + fileChooser.getSelectedFile());
        	return;
        }

        aggGraph = new AggGraph(graph);
    	int numCulled = aggGraph.cullEmptyNodes();
    	System.err.println("Culled " + numCulled + " empty nodes.");
        
    	String outFileName = fileChooser.getSelectedFile().getAbsolutePath() + ".dl";
        if (!generateDLFile(outFileName)) {
        	System.err.println("Failed to create DL file: " + outFileName);
        	return;
        }

        System.err.println("Successfully create DL file: " + outFileName);
	}