code: public static void plotCharts(List<Chart> charts){
  		int numRows =1;
  		int numCols =1;
  		if(charts.size()>1){
  			numRows = (int) Math.ceil(charts.size()/2.0);
  			numCols = 2;
  		}
  		
  	    final JFrame frame = new JFrame("");
  	    frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
          frame.getContentPane().setLayout(new GridLayout(numRows, numCols));
  	    for (Chart chart : charts) {
  	          if (chart != null) {
  	            JPanel chartPanel = new XChartPanel(chart);
  	            frame.add(chartPanel);
  	          }
  	          else {
  	            JPanel chartPanel = new JPanel();
  	            frame.getContentPane().add(chartPanel);
  	          }
  
  	        }
  	    // Display the window.
          frame.pack();
          frame.setVisible(true);
  	}
docs: Plots a list of charts in matrix with 2 columns.
  @param charts