Question

Mike is a consultant for the Department of Labor. One day he is analyzing the midyear

population of the United States, in thousands, during the years 1950 through 1990. He write

Population Class in java including a main method as the testing client. His next task is to

complete the entire class by adding:

1. A private field that can store a yearly population data as an integer array.

2. A constructor that can instantiate a Population object by using an external integer

array as the parameter.

3. A method that can return the average annual change in population during the time

period.

4. A method that can return the year with the greatest increase in population during the

time period

5. A method that can return the year with the smallest increase in population during the

time period

6. Some testing procedures in the testing client to verify the functionality of the above

methods.

Answer 1

Here is the code in java with test case with screenshot. I have used a very small dataset to test, please feel to add more data and test

========================================================================================

public class Population {

    //assuming it will be a 2D array, each row will
    // have year and population count
    private long[][] yearlyPopulation;

    public Population(long[][] yearlyPopulation) {
        this.yearlyPopulation = yearlyPopulation;
    }

    public double averageAnnualChange() {

        long initialCount = yearlyPopulation[0][1];
        long finalCount = yearlyPopulation[yearlyPopulation.length - 1][1];

        double averageChange = (finalCount - initialCount) / yearlyPopulation.length;
        return averageChange;

    }

    public long yearWithGreatestIncrease() {

        long year = 0;
        long change = Long.MIN_VALUE;

        for (int i = 1; i < yearlyPopulation.length; i++) {
            long previousYear = yearlyPopulation[i - 1][1];
            long currentYear = yearlyPopulation[i][1];
            long diff = currentYear - previousYear;
            if (diff > 0 && diff > change) {
                change = diff;
                year = yearlyPopulation[i][0];
            }
        }
        return year;
    }

    public long yearWithSmallestIncrease() {
        long year = 0;
        long change = Long.MAX_VALUE;

        for (int i = 1; i < yearlyPopulation.length; i++) {
            long previousYear = yearlyPopulation[i - 1][1];
            long currentYear = yearlyPopulation[i][1];
            long diff = currentYear - previousYear;
            if (diff > 0 && diff < change) {
                change = diff;
                year = yearlyPopulation[i][0];
            }
        }
        return year;
    }

    public static void main(String[] args) {

        long[][] population = {{2000, 34000000}, {2001, 34001234},
                {2002, 35000000}, {2003, 36000000}, {2004, 36000001},
                {2005, 3700000}, {2006, 38007000}, {2007, 39000333},
                {2008, 44000000}, {2009, 44005000}, {2010, 45000000}};

        Population sensus = new Population(population);
        System.out.println("Average change: " + sensus.averageAnnualChange());
        System.out.println("Year with greatest increase: " + sensus.yearWithGreatestIncrease());
        System.out.println("Year with smallest increase: " + sensus.yearWithSmallestIncrease());

    }

}

========================================================================================