Calculating Average from a CSV File

Question

I have a CSV file, format as follows:

City,Job,Salary Delhi,Doctors,500 Delhi,Lawyers,400 Delhi,Plumbers,100 London,Doctors,800 London,Lawyers,700 London,Plumbers,

Answer 1

First, use a CSV parser - I will use OpenCSV in this example. I have no affiliation with OpenCSV, it's just what I have in my POM at the moment.

First, create a class:

public class Salary {
    private String city;
    private String job;
    private long salary;

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getJob() {
        return job;
    }

    public void setJob(String job) {
        this.job = job;
    }

    public long getSalary() {
        return salary;
    }

    public void setSalary(long salary) {
        this.salary = salary;
    }
}

Now your CSV has three columns, and the header of the CSV matches the property names of our bean, so we can simply use a HeaderColumnNameMappingStrategy to determine which properties to set on the bean:

final HeaderColumnNameMappingStrategy mappingStrategy = new HeaderColumnNameMappingStrategy<>();
mappingStrategy.setType(Salary.class);

Now we just need to parse the CSV file into a List of our beans:

final CsvToBean csvToBean = new CsvToBean<>();
try (final Reader reader = ...) {
    final List salaries = csvToBean.parse(mappingStrategy, reader);
}

Okay.

Now, how do you get an average salary from this mess? Just use a Java 8 Stream on the result:

    final LongSummaryStatistics statistics = salaries.stream()
            .mapToLong(Salary::getSalary)
            .summaryStatistics();

Now we can get all sorts of useful information:

final long min = statistics.getMin();
final double average = statistics.getAverage();
final long max = statistics.getMax();