CODEWITHSUNDEEP
javasortingarraylistexport-to-csv
e102
e102

Reputation: 27

Java - write to a .csv file after sorting an arraylist of objects

I have an arraylist of object type: public static ArrayList crimes = new ArrayList();

The CityCrime.java has the following:

    public class CityCrime {


//Instance variables

private String city;
private String state;
private int population;
private int murder;
private int robbery;
private int assault;
private int burglary;
private int larceny;
private int motorTheft;
public int totalCrimes;

public static void main(String[] args) {
    
}

public int getTotalCrimes() {
    return totalCrimes;
}

public void setTotalCrimes(int murder, int robbery, int assault, int burglary, int larceny, int motorTheft) {
    this.totalCrimes = murder + robbery + assault + burglary + larceny + motorTheft;
}

public String getCity() {
    return city;
}


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

public String getState() {
    return state;
}


public void setState(String state) {
    if(state.equalsIgnoreCase("ALABAMA")) {
        this.state = "AL";
    }
    else if(state.equalsIgnoreCase("ALASKA")) {
        this.state = "AK";
    }
    else if(state.equalsIgnoreCase("ARIZONA")) {
        this.state = "AR";
    }
    //etc
}

public int getPopulation() {
    return population;
}


public void setPopulation(int population) {
    this.population = population;

}


public int getMurder() {
    return murder;
}


public void setMurder(int murder) {
    this.murder = murder;
}


public int getRobbery() {
    return robbery;
}


public void setRobbery(int robbery) {
    this.robbery = robbery;

}


public int getAssault() {
    return assault;
}


public void setAssault(int assault) {
    this.assault = assault;

}


public int getBurglary() {
    return burglary;
}


public void setBurglary(int burglary) {
    this.burglary = burglary;

}


public int getLarceny() {
    return larceny;
}


public void setLarceny(int larceny) {
    this.larceny = larceny;
}


public int getMotorTheft() {
    return motorTheft;
}


public void setMotorTheft(int motorTheft) {
    this.motorTheft = motorTheft;

}

public static void showAllMurderDetails() {

    for (CityCrime crime : StartApp.crimes) {
        System.out.println("Crime: City= " + crime.getCity() + ", Murder= " + crime.getMurder());
    }
    System.out.println();
}


public static int showAllViolentCrimes() {
    int total = 0;
    for(CityCrime crime : StartApp.crimes) {
        total=total+crime.getMurder();
        total=total+crime.getRobbery();
        total=total+crime.getAssault();
    }
    System.out.println("Total of violent crimes: " + total);
    return total;
    
}

public static int getPossessionCrimes() {
    int total=0;
    for (CityCrime crime : StartApp.crimes) {
        total = total + crime.getBurglary();
        total = total + crime.getLarceny();
        total = total + crime.getMotorTheft();
    }
    System.out.println("Total of possession crimes: " + total);
    return total;
}

}

The CityCrime ArrayList gets popular from another csv file: public static void readCrimeData() {

    File file = new File("crimeUSA.csv");

    FileReader fileReader;
    BufferedReader bufferedReader;
    String crimeInfo;
    String[] stats;

    try {
        fileReader = new FileReader(file);
        bufferedReader = new BufferedReader(fileReader);

        crimeInfo = bufferedReader.readLine();
        crimeInfo = bufferedReader.readLine();

        do {
            CityCrime crime = new CityCrime(); // Default constructor
            stats = crimeInfo.split(",");
            {
                if (stats[0] != null) {
                    crime.setCity(stats[0]);
                }
                if (stats[1] != null) {
                    crime.setState(stats[1]);
                }
                if (stats[2] != null) {
                    if (Integer.parseInt(stats[2]) >= 0) {
                        crime.setPopulation(Integer.parseInt(stats[2]));
                    }
                }
                if (stats[3] != null) {
                    if (Integer.parseInt(stats[3]) >= 0) {
                        crime.setMurder(Integer.parseInt(stats[3]));
                    }
                }

                if (stats[4] != null) {
                    if (Integer.parseInt(stats[4]) >= 0) {
                        crime.setRobbery(Integer.parseInt(stats[4]));
                    }
                }

                if (stats[5] != null) {
                    if (Integer.parseInt(stats[5]) >= 0) {
                        crime.setAssault(Integer.parseInt(stats[5]));
                    }
                }

                if (stats[6] != null) {
                    if (Integer.parseInt(stats[6]) >= 0) {
                        crime.setBurglary(Integer.parseInt(stats[6]));
                    }
                }

                if (stats[7] != null) {
                    if (Integer.parseInt(stats[7]) >= 0) {
                        crime.setLarceny(Integer.parseInt(stats[7]));
                    }
                }

                if (stats[8] != null) {
                    if (Integer.parseInt(stats[8]) >= 0) {
                        crime.setMotorTheft(Integer.parseInt(stats[8]));
                    }
                }
                crime.setTotalCrimes(Integer.parseInt(stats[3]), Integer.parseInt(stats[4]), Integer.parseInt(stats[5]), Integer.parseInt(stats[6]), Integer.parseInt(stats[7]), Integer.parseInt(stats[8]));

            }
            crimes.add(crime);
            System.out.println(crime);

            crimeInfo = bufferedReader.readLine();

        } while (crimeInfo != null);

        fileReader.close();
        bufferedReader.close();

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (NumberFormatException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }

I want to sort the array list and output to the csv file the list of robberies in descending order with the corresponding city. So far I have got the following, but I am stuck and not sure if going in the right direction. I'm relatively new to Java as you can probably tell so would appreciate it in as simple terms as can be:

    public static void writeToFile() throws IOException {
    File csvFile = new File("Robbery.csv");
    FileWriter fileWriter = new FileWriter(csvFile);
    ArrayList<Integer> robberyRates = new ArrayList();
    for(CityCrime crime : crimes) {
        robberyRates.add(crime.getRobbery());
    }
    Collections.sort(robberyRates);

}

The desired output will be for example:

Robbery,City

23511,New York

15863,Chicago

14353,Los Angeles

11371,Houston

10971,Philadelphia

etc…

Your help is appreciated. I have searched any page I can find on Google, but all I see from other example is writing to the csv from a set String ArrayList where they know the number of lines etc. Thankyou

Upvotes: 0

Views: 707

Answers (1)

Oromis
Oromis

Reputation: 316

You can try something like this:

public static void writeToFile() throws IOException {
        File csvFile = new File("Robbery.csv");
        try(FileWriter fileWriter = new FileWriter(csvFile)) { // try-with-resources to be sure that fileWriter will be closed at end
            StringBuilder stringBuilder = new StringBuilder(); // Betther than String for multiple concatenation
            crimes.sort(Comparator.comparingInt(CityCrime::getRobbery).reversed()); // I want to compare according to getRobbery, as Int, in reversed order

            stringBuilder.append("Robbery")
                    .append(',')
                    .append("City")
                    .append(System.lineSeparator()); // To get new line character according to OS
            for (final var crime : crimes)
                stringBuilder.append(crime.getRobbery())
                        .append(',')
                        .append(crime.getCity())
                        .append(System.lineSeparator());

            fileWriter.write(stringBuilder.toString());
        }
    }

If you are stuck because you can't figure out how to write a list, convert your list into a String and print the String instead.

I commented the piece of code, if you have any questions, don't hesitate.

Another solution is to use specific CSV parser library, OpenCSV for example. It makes it easier to read and write CSV file.
Here a tutorial about OpenCSV: https://mkyong.com/java/how-to-read-and-parse-csv-file-in-java/

Upvotes: 1

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