Scatter charts also use the XYChart.Series class in JavaFX. For this example, we will use a set of European data that includes the previous Europeans countries and their population data for the decades 1500 through 2000. This information is stored in a file called EuropeanScatterData.csv. The first part of this file is shown here:

1500 1400000
1600 1600000
1650 1500000
1700 2000000
1750 2250000
1800 3250000
1820 3434000
1830 3750000
1840 4080000
...

We start with the declaration of the JavaFX MainApp class, as shown next. The main method launches the application and the start method creates the user interface:

public class MainApp extends Application { 
    @Override 
    public void start(Stage stage) throws Exception { 
        ... 
    } 
 
    public static void main(String[] args) { 
        launch(args); 
    } 
} 

Within the start method we set the title, create the axes, and create an instance of the ScatterChart that represents the scatter plot. The NumberAxis class's constructors used values that better match the data range than the default values used by its default constructor:

stage.setTitle("Scatter Chart Sample"); 
final NumberAxis yAxis = new NumberAxis(1400, 2100, 100); 
final NumberAxis xAxis = new NumberAxis(500000, 90000000, 
    1000000); 
final ScatterChart<Number, Number> scatterChart = new  
    ScatterChart<>(xAxis, yAxis); 

Next, the axes' labels are set along with the scatter chart's title:

xAxis.setLabel("Population"); 
yAxis.setLabel("Decade"); 
scatterChart.setTitle("Population Scatter Graph"); 

An instance of the XYChart.Series class is created and named:

XYChart.Series series = new XYChart.Series(); 

The series is populated using a CSVReader class instance and the file EuropeanScatterData.csv. This process was discussed in Chapter 3, Data Cleaning:

try (CSVReader dataReader = new CSVReader(new FileReader("EuropeanScatterData.csv"), ',')) { 
    String[] nextLine; 
    while ((nextLine = dataReader.readNext()) != null) { 
            int decade = Integer.parseInt(nextLine[0]); 
            int population = Integer.parseInt(nextLine[1]); 
            series.getData().add(new XYChart.Data( 
                population, decade)); 
            out.println("Decade: " + decade +  
                "  Population: " + population); 
    } 
} 
scatterChart.getData().addAll(series); 

The JavaFX scene and stage are created, and then the plot is displayed:

Scene scene = new Scene(scatterChart, 500, 400); 
stage.setScene(scene); 
stage.show(); 

When the application is executed, the following graph is displayed: