code: private static void addBuySellSignals(TimeSeries series, Strategy strategy, XYPlot plot) {
          // Running the strategy
          TimeSeriesManager seriesManager = new TimeSeriesManager(series);
          List<Trade> trades = seriesManager.run(strategy).getTrades();
          // Adding markers to plot
          for (Trade trade : trades) {
              // Buy signal
              double buySignalTickTime = new Minute(Date.from(series.getTick(trade.getEntry().getIndex()).getEndTime().toInstant())).getFirstMillisecond();
              Marker buyMarker = new ValueMarker(buySignalTickTime);
              buyMarker.setPaint(Color.GREEN);
              buyMarker.setLabel("B");
              plot.addDomainMarker(buyMarker);
              // Sell signal
              double sellSignalTickTime = new Minute(Date.from(series.getTick(trade.getExit().getIndex()).getEndTime().toInstant())).getFirstMillisecond();
              Marker sellMarker = new ValueMarker(sellSignalTickTime);
              sellMarker.setPaint(Color.RED);
              sellMarker.setLabel("S");
              plot.addDomainMarker(sellMarker);
          }
      }
docs: Runs a strategy over a time series and adds the value markers
  corresponding to buy/sell signals to the plot.
  @param series a time series
  @param strategy a trading strategy
  @param plot the plot