Generating fake data can be a common need when developing applications or loading test data into a database. jFairy is a great fake data generator library built in Java that is very easy to use. jFairy allows you to build data sets containing diverse types of data including names, addresses, telephone numbers, dates, large integers, usernames, email addresses, and a lot more.

Below is an example from the Big Datums GitHub repo that uses jFairy to create a tabular data set with 10,000 records. The genPeopleData() method outputs a fixed structure of personal type data, but allows users to specify the number of records, the field delimiters, and whether or not to include a header or enclose fields with quotes.

package com.bigdatums.datagen;

import org.jfairy.Fairy;
import org.jfairy.producer.BaseProducer;
import org.jfairy.producer.DateProducer;
import org.jfairy.producer.net.NetworkProducer;
import org.jfairy.producer.person.Person;

import java.util.ArrayList;
import java.util.List;

public class BdDataGen {

    private Fairy fairy = Fairy.create();

    private String addOuterQuotes(String line){
        return "\"" + line + "\"";
    }

    public String[] genPeopleData(int numLines, boolean addHeader, boolean encloseWithQuotes, String delimiter){

        List<String> header;
        String out;
        int fields = 12;
        int lineStart = 0;
        String[] lines = new String[numLines];
        if(encloseWithQuotes) delimiter = "\"" + delimiter + "\"";

        if(addHeader) {
            header = new ArrayList<String>();
            header.add("id");
            header.add("username");
            header.add("email_address");
            header.add("phone_number");
            header.add("first_name");
            header.add("last_name");
            header.add("middle_name");
            header.add("sex");
            header.add("birthdate");
            header.add("join_date");
            header.add("previous_logins");
            header.add("last_ip");

            out = String.join(delimiter, header);
            if(encloseWithQuotes) out = addOuterQuotes(out);
            lines[0] = out;
            lineStart = 1;
        }

        for(int i=lineStart; i<numLines; i++){

            String[] line = new String[fields];

            Person person = fairy.person();
            DateProducer dp = fairy.dateProducer();
            BaseProducer bp = fairy.baseProducer();
            NetworkProducer np = fairy.networkProducer();

            line[0] = Integer.toString(i);
            line[1] = person.username();
            line[2] = person.email();
            line[3] = person.telephoneNumber();
            line[4] = person.firstName();
            line[5] = person.lastName();
            line[6] = person.middleName();
            line[7] = person.sex().name();
            line[8] = person.dateOfBirth().toLocalDate().toString();
            line[9] = dp.randomDateBetweenYearAndNow(2005).toString();
            line[10] = Integer.toString(bp.randomBetween(1,10000));
            line[11] = np.ipAddress();

            out = String.join(delimiter, line);
            if(encloseWithQuotes) out = addOuterQuotes(out);
            lines[i] = out;
        }

        return lines;

    }

    public static void main(String[] args){
        BdDataGen bd = new BdDataGen();
        String[] output = bd.genPeopleData(10000, false, false, "\t");

        for(int i=0; i<output.length; i++){
            System.out.println(output[i]);
        }
    }

}