Write a program to produce animated bar charts like the one below. As this is the last programming assignment in the course, we also include two open-ended questions.

  1. Bar data type. A bar aggregates related information (name, value, and category) for use in a bar chart. For example, the first bar drawn in the bar chart represents name = Beijing, value = 672, and category = East Asia. In addition to methods for accessing the individual fields, you will need to sort bars in order of value. Implement the following API:
    public class Bar implements Comparable<Bar> {
        // Creates a new bar.
        public Bar(String name, int value, String category)
        // Returns the name of this bar.
        public String getName()
        // Returns the value of this bar.
        public int getValue()
        // Returns the category of this bar.
        public String getCategory()
        // Compare two bars by value.
        public int compareTo(Bar that)
        // Sample client (see below).
        public static void main(String[] args)

    Sorting arrays of objects. To sort an array of objects, use Java’s Arrays.sort() method. For example, the following code fragment creates an array of 10 bars and sorts them in ascending order of value.

    // create an array of 10 bars
    Bar[] bars = new Bar[10];
    bars[0] = new Bar("Beijing",     22674, "East Asia");
    bars[1] = new Bar("Cairo",       19850, "Middle East");
    bars[2] = new Bar("Delhi",       27890, "South Asia");
    bars[3] = new Bar("Dhaka",       19633, "South Asia");
    bars[4] = new Bar("Mexico City", 21520, "Latin America");
    bars[5] = new Bar("Mumbai",      22120, "South Asia");
    bars[6] = new Bar("Osaka",       20409, "East Asia");
    bars[7] = new Bar("São Paulo",   21698, "Latin America");
    bars[8] = new Bar("Shanghai",    25779, "East Asia");
    bars[9] = new Bar("Tokyo",       38194, "East Asia");
    // sort in ascending order by weight

    Comparable interface. In order to use a data type with Arrays.sort(), that data type must be comparable. This is Java’s mechanism for specifying a total order among objects of a given type. To make a data type comparable, you must implement the Comparable interface, which involves doing two things:

    Corner cases. Handle invalid argument in the following manner:

  2. Bar chart data type. We provide a simple data type BarChart.java that supports drawing static bar charts to standard draw. The purpose of this step is solely to familiarize yourself with its API:

    public class BarChart {
        // Creates a bar chart with the given title, x-axis label, and data source.
        public BarChart(String title, String xAxisLabel, String dataSource)
        // Sets the caption of this bar chart.
        public void setCaption(String caption)
        // Adds a bar (name, value, category) to this bar chart.
        public void add(String name, int value, String category)
        // Remove all of the bars from this bar chart.
        public void reset() 
        // Draws this bar chart to standard draw.
        public void draw() 

    The following code fragment illustrates the API by drawing a bar chart with 10 bars. Note that the bars are drawn in the same order in which they are added to the bar chart (from top to bottom).

    a static bar chart

    // create the bar chart
    String title = "The 10 most populous cities";
    String xAxis = "Population (thousands)";
    String source = "Source: United Nations";
    BarChart chart = new BarChart(title, xAxis, source);
    // add the bars to the bar chart
    chart.add("Tokyo",       38194, "East Asia");
    chart.add("Delhi",       27890, "South Asia");
    chart.add("Shanghai",    25779, "East Asia");
    chart.add("Beijing",     22674, "East Asia");
    chart.add("Mumbai",      22120, "South India");
    chart.add("São Paulo",   21698, "Latin America");
    chart.add("Mexico City", 21520, "Latin America");
    chart.add("Osaka",       20409, "East Asia");
    chart.add("Cairo",       19850, "Middle East");
    chart.add("Dhaka",       19633, "South Asia");
    // draw the bar chart
    StdDraw.setCanvasSize(1000, 700);

  3. Bar chart racer. Write a program to produce animated bar charts, using BarChart.java to draw static bar charts.

    As a canonical example, consider an animated bar chart of the 10 most populous cities in the world, from 1500 to 2018. To produce the visualization, you will successively draw 519 individual bar charts (one per year of data), with a short pause between each drawing. Each bar chart contains the 10 most populous cities in that year, arranged in descending order of population.

    Bar Chart Racer file format File format. A bar-chart-racer data file is organized as a sequence of lines. The first three lines comprise the header:

    Following the header is a blank line, followed by the raw data. Each line (or record) consists of 5 fields, separated by commas:

    The value field is an integer; the other fields can be arbitrary strings (except that they can’t contain commas or newlines).

    Records corresponding to the same year (or time period) are grouped together. A group of records consists of an integer \(n\), followed by \(n\) records. Within a group, the records are sorted by name. A blank line separates each group.

    Data files. We supply a number of fascinating data files in the specified format, curated from various sources.

    input file description period data source
    cities.txt most populous cities in the world 1500–2018 John Burn-Murdoch
    countries.txt most populous countries in the world 1950–2100 United Nations
    cities-usa.txt most populous cities in the U.S. 1790-2018 U.S. Census Bureau
    brands.txt most valuable brands in the world 2000–2018 Interbrand
    movies.txt highest-grossing movies in the U.S. 1982–2019 Box Office Mojo
    baby-names.txt most popular baby names in the U.S. 1880–2018 U.S. Social Security
    football.txt the best football clubs in Europe 1960–2019 clubelo.com
    game-of-thrones.txt characters in Game of Thrones by screen time S01E01–S08E06 Preetish
    endgame.txt characters in Endgame by screen time Minute 1–170 Prashant
    infinity-war.txt characters in Infinity War by screen time Minute 1–132 Prashant
    trademarks.txt trademarks granted by country 1980–2018 WIPO
    patents.txt patents granted by country 1980–2018 WIPO

    Soundtrack (optional). If you would like a musical accompaniment to your animated bar chart, add the following line at the beginning of your program:

    Feel free to substitute a different .wav file.

    Command-line arguments. The program takes two command-line arguments: the name of a bar-chart-racer file and an integer \(k\) that specifies how many bars to display in each bar chart. Here are some sample executions:

    ~/Desktop/barchart> java-introcs BarChartRacer cities.txt 10
    ~/Desktop/barchart> java-introcs BarChartRacer brands.txt 15
    ~/Desktop/barchart> java-introcs BarChartRacer movies.txt 10
    ~/Desktop/barchart> java-introcs BarChartRacer endgame.txt 10

  4. Curate a bar chart racer data file (ungraded). Create a data file in the given format from a subject of interest to you. The data can be international or specific to your country or region. Curating a data file typically involves several steps:

    Create a plan to update and maintain your data file when new data becomes available from the data source.

  5. Bar chart racer II (ungraded). Learn a new programming language (such as Python, C++, C#, C, Javascript, Swift, Go, Scala, Kotlin, Ruby, Rust, R, or Matlab) and create an animated bar chart in that language.

Submission. Submit a .zip file containing Bar.java and BarChartRacer.java.

This assignment was developed by Kevin Wayne, inspired by tweets from Matt Navarra and John Burn-Murdoch.
Copyright © 2019.