Creating bar charts

A bar chart uses two axes with rectangular bars that can be either positioned either vertically or horizontally. The length of a bar is proportional to the value it represents. A bar chart can be used to show time series data.

In the following series of examples, we will be using a set of European country populations for three decades, as listed in the following table. The data is a subset of population data found at https://ourworldindata.org/grapher/population-by-country?tab=data:

The first of three bar charts will be constructed using JavaFX. We start with a series of declarations for the countries as part of a class that extends the Application class:

public class MainApp extends Application { 
    final static String belgium = "Belgium"; 
    final static String france = "France"; 
    final static String germany = "Germany"; 
    final static String netherlands = "Netherlands"; 
    final static String sweden = "Sweden"; 
    final static String unitedKingdom = "United Kingdom"; 

... 
} 

Next, we declared a series of instance variables that represent the parts of a graph. The first are CategoryAxis and NumberAxis instances:

final CategoryAxis xAxis = new CategoryAxis(); 
final NumberAxis yAxis = new NumberAxis(); 

The population and country data is stored in a series of XYChart.Series instances. Here, we have declared six different series, which use a string and number pair. The first example does not use all six series, but later examples will. We will initially assign a country string and its corresponding population to three series. These series will represent the populations for the decades 1950, 1960, and 1970:

final XYChart.Series<String, Number> series1 =  
    new XYChart.Series<>(); 
final XYChart.Series<String, Number> series2  
    new XYChart.Series<>(); 
final XYChart.Series<String, Number> series3 =  
    new XYChart.Series<>(); 
final XYChart.Series<String, Number> series4 =  
    new XYChart.Series<>(); 
final XYChart.Series<String, Number> series5 =  
    new XYChart.Series<>(); 
final XYChart.Series<String, Number> series6 =  
    new XYChart.Series<>(); 

We will start with two simple bar charts. The first one will show the countries as categories where the year changes occur within the category on the X axis and the population along the Y axis. The second shows the decades as categories containing the counties. The last example is a stacked bar chart.