JavaFX - Bubble Chart

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A bubble chart is used to plant three-dimensional data; the third dimension will be represented by the size (radius) of the bubble.

The following is a Bubble chart depicting the work done.

Bubble Chart in JavaFX

In JavaFX, a Bubble chart is represented by a class named BubbleChart. This class belongs to the package javafx.scene.chart. By instantiating this class, you can create an BubbleChart node in JavaFX.

To generate a bubble chart in JavaFX, follow the steps given below.

Step 1: Defining the Axis

Define the X and Y axis of the bubble chart and set labels to them. In our example, X axis represents the age, Y axis represents the weight. While, the radius of the bubble represents the work done.

public class ClassName extends Application {  
   @Override     
   public void start(Stage primaryStage) throws Exception {
      //Defining the X axis               
      NumberAxis xAxis = new NumberAxis(0, 100, 10);        
      xAxis.setLabel("Age");  

      //Defining Y axis        
      NumberAxis yAxis = new NumberAxis(20, 100, 10); 
      yAxis.setLabel("Weight");
   }    
 }

Step 2: Creating the Bubble Chart

Create a line chart by instantiating the class named BubbleChart of the package javafx.scene.chart. To the constructor of this class, pass the objects representing the X and Y axis created in the previous step.

//Creating the Bubble chart 
BubbleChart bubbleChart = new BubbleChart(xAxis, yAxis);

Step 3: Preparing the Data

Instantiate the XYChart.Series class and add the data (a series of, x and y coordinates) to the Observable list of this class as follows −

//Prepare XYChart.Series objects by setting data        
XYChart.Series series = new XYChart.Series();  
series.setName("work");  

series.getData().add(new XYChart.Data(10,30,4));  
series.getData().add(new XYChart.Data(25,40,5)); 
series.getData().add(new XYChart.Data(40,50,9)); 
series.getData().add(new XYChart.Data(55,60,7));    
series.getData().add(new XYChart.Data(70,70,9));        
series.getData().add(new XYChart.Data(85,80,6)); 

Step 4: Add Data to the Bubble Chart

Add the data series prepared in the previous step to the area chart as follows −

//Setting the data to bar chart        
bubbleChart.getData().add(series); 

Step 5: Creating a Group Object

In the start() method, create a group object by instantiating the class named Group. This belongs to the package javafx.scene.

Pass the BubbleChart (node) object, created in the previous step as a parameter to the constructor of the Group class. This should be done in order to add it to the group as follows −

Group root = new Group(bubbleChart);

Step 6: Launching Application

Lastly, follow the given steps below to launch the application properly −

• Firstly, instantiate the class named Scene by passing the Group object as a parameter value to its constructor. To this constructor, you can also pass dimensions of the application screen as optional parameters.

• Then, set the title to the stage using the setTitle() method of the Stage class.

• Now, a Scene object is added to the stage using the setScene() method of the class named Stage.

• Display the contents of the scene using the method named show().

• Lastly, the application is launched with the help of the launch() method.

Example

Let us consider different persons along with their age, weight and work capacities. The work capacity can be treated as the number of hours that is plotted as bubbles in the chart.

Following is a Java program which generates a bubble chart, depicting the above data using JavaFX.

Save this code in a file with the name BubbleChartExample.java.

import javafx.application.Application; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.scene.chart.BubbleChart; 
import javafx.stage.Stage;  
import javafx.scene.chart.NumberAxis; 
import javafx.scene.chart.XYChart; 
         
public class BubbleChartExample extends Application { 
   @Override 
   public void start(Stage stage) {     
      //Defining the axes               
      NumberAxis xAxis = new NumberAxis(0, 100, 10);        
      xAxis.setLabel("Age"); 
        
      NumberAxis yAxis = new NumberAxis(20, 100, 10); 
      yAxis.setLabel("Weight"); 
      
      //Creating the Bubble chart 
      BubbleChart bubbleChart = new BubbleChart(xAxis, yAxis);    
         
      //Prepare XYChart.Series objects by setting data        
      XYChart.Series series = new XYChart.Series();  
      series.setName("work"); 
         
      series.getData().add(new XYChart.Data(10,30,4));  
      series.getData().add(new XYChart.Data(25,40,5)); 
      series.getData().add(new XYChart.Data(40,50,9)); 
      series.getData().add(new XYChart.Data(55,60,7));    
      series.getData().add(new XYChart.Data(70,70,9));        
      series.getData().add(new XYChart.Data(85,80,6));
      
      //Setting the data to bar chart         
      bubbleChart.getData().add(series); 
         
      //Creating a Group object  
      Group root = new Group(bubbleChart); 
         
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 400);  
      
      //Setting title to the Stage 
      stage.setTitle("Bubble Chart"); 
         
      //Adding scene to the stage 
      stage.setScene(scene); 
         
      //Displaying the contents of the stage 
      stage.show();         
   }  
   public static void main(String args[]){ 
      launch(args); 
   } 
}

Compile and execute the saved java file from the command prompt using the following commands.

javac --module-path %PATH_TO_FX% --add-modules javafx.controls BubbleChartExample.java 
java --module-path %PATH_TO_FX% --add-modules javafx.controls BubbleChartExample

Output

On executing, the above program generates a JavaFX window displaying a bubble chart as shown below.

Example

The following table depicts the number of schools that were in an area from the year 1970 to 2014.

Following is a Java program which generates a bubble chart, depicting the above data using JavaFX.

Save this code in a file with the name BubbleChartSchools.java.

import javafx.application.Application; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.stage.Stage; 
import javafx.scene.chart.BubbleChart; 
import javafx.scene.chart.NumberAxis; 
import javafx.scene.chart.XYChart; 
         
public class BubbleChartSchools extends Application { 
   @Override 
   public void start(Stage stage) {
      //Defining the x axis             
      NumberAxis xAxis = new NumberAxis(1960, 2020, 10); 
      xAxis.setLabel("Years"); 
        
      //Defining the y axis   
      NumberAxis yAxis = new NumberAxis(20, 320, 20); 
      yAxis.setLabel("No.of schools"); 
        
      //Creating the Bubble chart 
      BubbleChart bubblechart = new BubbleChart(xAxis, yAxis);  
        
      //Prepare XYChart.Series objects by setting data
      XYChart.Series series = new XYChart.Series(); 
      series.setName("No of schools in an year"); 
      // Add a third coordinate representing the radius of bubble
      series.getData().add(new XYChart.Data(1970, 25, 1)); 
      series.getData().add(new XYChart.Data(1980, 30, 2)); 
      series.getData().add(new XYChart.Data(1990, 60, 3)); 
      series.getData().add(new XYChart.Data(2000, 120, 4)); 
      series.getData().add(new XYChart.Data(2013, 240, 5)); 
      series.getData().add(new XYChart.Data(2014, 300, 6)); 
            
      //Setting the data to bubble chart    
      bubblechart.getData().add(series);        
        
      //Creating a Group object  
      Group root = new Group(bubblechart); 
         
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 400);  
      
      //Setting title to the Stage 
      stage.setTitle("Bubble Chart"); 
         
      //Adding scene to the stage 
      stage.setScene(scene);
	   
      //Displaying the contents of the stage 
      stage.show();         
   } 
   public static void main(String args[]){ 
      launch(args); 
   } 
}

Compile and execute the saved java file from the command prompt using the following commands.

javac --module-path %PATH_TO_FX% --add-modules javafx.controls BubbleChartSchools.java 
java --module-path %PATH_TO_FX% --add-modules javafx.controls BubbleChartSchools

Output

On executing, the above program generates a JavaFX window displaying a bubble chart as shown below.