NaDl0l - Online Java Compiler & Debugging Tool

import java.text.*;
import java.util.*;

class Eveniment {
    private Date dataInceput, dataSfarsit;
    private String nume;
    // Primeste 2 stringuri in format yyyy-MM-dd HH:mm:ss reprezentand data si ora
    // de inceput si de final a evenimentului si inca un string care contine numele
    // cu care apare evenimentul in calendar
    public Eveniment(String dataInceput, String dataSfarsit, String nume) {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        try {
            this.dataInceput = format.parse(dataInceput);
            this.dataSfarsit = format.parse(dataSfarsit);
        } catch (Exception e) {
            System.out.println("Data nu este in formatul cerut!");
        }
        this.nume = nume;
    }

    public Date getDataInceput() {
        return dataInceput;
    }

    public Date getDataSfarsit() {
        return dataSfarsit;
    }

    public String getNume() {
        return nume;
    }
}

class EvenimentRecurent extends Eveniment {
    private int numarOre;

    public EvenimentRecurent(String dataInceput, String dataSfarsit, String nume, int numarOre) {
        super(dataInceput, dataSfarsit, nume);
        this.numarOre = numarOre;
    }

    public String urmatorulEveniment(String dataEveniment) {
        SimpleDateFormat formatRecurent = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        try {
            Date timpInceputDate = formatRecurent.parse(formatRecurent.format(getDataInceput()));
            Date timpSpecificDate = formatRecurent.parse(dataEveniment);

            Calendar calendarCurent = Calendar.getInstance();
            calendarCurent.setTime(timpInceputDate);

            Calendar calendarSpecific = Calendar.getInstance();
            calendarSpecific.setTime(timpSpecificDate);

            long oreDiferenta = (calendarSpecific.getTimeInMillis() - calendarCurent.getTimeInMillis()) / (60 * 60 * 1000);
            long multiplu = oreDiferenta / numarOre;

            calendarCurent.add(Calendar.HOUR_OF_DAY, (int) (multiplu * numarOre));

            if (calendarCurent.getTime().before(timpSpecificDate) || calendarCurent.getTime().equals(timpSpecificDate)) {
                calendarCurent.add(Calendar.HOUR_OF_DAY, numarOre);
            }

            return formatRecurent.format(calendarCurent.getTime());

        } catch (Exception e) {
            System.out.println("Data nu este in formatul cerut!");
            return null;
        }
    }
}

public class Main {
    public static void main(String[] args) {
        EvenimentRecurent er = new EvenimentRecurent("2019-03-09 22:46:00",
                "2019-03-09 23:00:00", "Scris probleme", 24);
        System.out.println(er.urmatorulEveniment("2019-04-19 22:46:23"));
        // 2019-04-20 22:46:00
    }
}