JavaFX - Charts

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In general, a chart is a graphical representation of data. There are various kinds of charts to represent data such as Bar Chart, Pie Chart, Line Chart, Scatter Chart, etc.

JavaFX Provides support for various Pie Charts and XY Charts. The charts that are represented on an XY–plane include AreaChart, BarChart, BubbleChart, LineChart, ScatterChart, StackedAreaChart, StackedBarChart, etc.

Each chart is represented by a class and all these charts belongs to the package javafx.scene.chart. The class named Chart is the base class of all the charts in JavaFX and the XYChart is base class of all those charts that are drawn on the XY–plane.

Creating a Chart in JavaFX

To create a chart in JavaFX, you need to perform the following steps −

• Define the axis of the chart
• Instantiate the respective class
• Prepare and pass data to the chart

Instantiating the Respective Class

To create a chart, instantiate its respective class. For example, if you want to create a line chart, you need to instantiate the class named LineChart as follows −

LineChart linechart = new LineChart(xAxis, yAxis);

As observed in the above code, while instantiating, you need to pass two objects representing the X and Y axis of the chart respectively.

Defining the Axis

In general, the axis of the charts can be represented by −

• Numbers such as Population, Age and
• Categories such as Days in a Week, Countries.

In JavaFX, an axis is an abstract class representing X or Y axis. It has two subclasses to define each type of axis, namely CategoryAxis and NumberAxis as shown in the following diagram −

Category Axis:

By instantiating this class, you can define (create) an X or Y axis along which each value represents a category. You can define a Category axis by instantiating this class as shown below −

CategoryAxis xAxis = new CategoryAxis();

To this axis, you need set the list of categories and label to the axis as shown below −

//setting the list of categories.  
xAxis.setCategories(FXCollections.<String>observableArrayList
   (Arrays.asList("n ame1", "name2"....)));  

//Setting label to the axis  
xAxis.setLabel("name of the axis ");

NumberAxis:

By instantiating this class, you can define (create) an X or Y axis along which each value represents a Numerical value. You can use any Number type with this Axis, Long, Double, BigDecimal, etc. You can define a Number axis by instantiating this class as follows −

//Defining the axis 
NumberAxis yAxis = new NumberAxis();  

//Setting labelto the axis 
yAxis.setLabel("name of the axis");

Passing Data to XY Charts

All the XY charts are represented along the XY plane. To plot a set of points in a chart, we need to specify a series of XY coordinates.

The <X,Y> class of the javafx.scene.chart package is a class using which, you can send data to a chart. This class holds an observable list of named series. You can get this list using the getData() method of XYChart.Series class as shown below −

ObservableList list = series.getData();

Where, series is the object of the XYChart.Series class. You can add data to this list using the add() method as follows −

list.add(new XYChart.Data(x-axis data, y-axis data));

These two lines can be written together as shown below −

series.getData().add(new XYChart.Data(x-axis data, y-axis data));

Types of Charts in JavaFX

The following table gives a description of various charts (classes) provided by JavaFX −