Check if day x falls on a Saturday or Sunday

Question

I’m making a system that will be an Agenda, in this system has an option to repeat the commitment unless fortnightly, ie I save the commitment and the system will notify me every 15 days. But this commitment must not fall into sábado or domingo. How can I make this check?

For example as it is fortnightly if I add an appointment today it will save today and increment another 15 days if the result falls on a Saturday or Sunday it jumps and saves the commitment on Monday. That is, to check if the day of the week is Saturday or Sunday I have to spend a data(data futura) as parameter and on top of that date do the check

Answer 1

You can use Calendar even.

Demo (obviously half of the code can be removed as it is System.out.println...and also use SWITCH, finally...is only for demonstration purposes)

Main.java

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;

public class Main
{
    public static void main(String[] args)
    {
        try
        {
            Calendar data = Calendar.getInstance();
            //data.set(2015, Calendar.JULY, 5); // ou neste neste formato ao invés de usar o simpleFormat abaixo
            SimpleDateFormat simpleFormat = new SimpleDateFormat("dd/MM/yyyy");

            data.setTime(simpleFormat.parse("06/07/2015"));

            System.out.println("Data antes: " + simpleFormat.format(data.getTime()));
            data = checaFDS(data);
            System.out.println("Data apos: " + simpleFormat.format(data.getTime()));
        }
        catch (ParseException e)
        {
            e.printStackTrace();
        }
    }

    /**
     * Verifica se data á sábado ou domingo e acrescenta dias conforme necessário p/ retornar dia de semana.
     *
     * @param   data        Um objeto Calendar
     * @return  Calendar
     */
    public static Calendar checaFDS(Calendar data)
    {
        // se for domingo
        if (data.get(Calendar.DAY_OF_WEEK) == Calendar.SUNDAY)
        {
            data.add(Calendar.DATE, 1);
            System.out.println("Eh domingo, mudando data para +1 dias");
        }
        // se for sábado
        else if (data.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY)
        {
            data.add(Calendar.DATE, 2);
            System.out.println("Eh sabado, mudando data para +2 dias");
        }
        else
        {
            System.out.println("Eh dia de semana, mantem data");
        }
        return data;
    }

}

Saturday (04/07/2015)

Sunday (05/07/2015)

Weekday (06/07/2015)

Answer 2

The key is to use the u in the pattern of SimpleDateFormat, as in the code:

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

public class ProximoDiaDaSemana {

    private static DateFormat DIA_DA_SEMANA = new SimpleDateFormat("u");

    private static long MILISEGUNDOS_EM_UM_DIA = 24 * 60 * 60 * 1000;

    private static int DOMINGO = 7;

    private static int SABADO = 6;

    private static int diferencaSabadoOuDomingo(int diaDaSemana) {
        if (diaDaSemana == DOMINGO) {
            return 1;
        }
        if (diaDaSemana == SABADO) {
            return 2;
        }
        return 0;
    }

    private static Date obterDataProximoCompromisso(Date dataInicial, int dias) {
        Date daquiXDias = new Date(dataInicial.getTime() + dias * MILISEGUNDOS_EM_UM_DIA);
        int diferencaSabadoOuDomingo = diferencaSabadoOuDomingo(Integer.valueOf(DIA_DA_SEMANA.format(daquiXDias)));
        if (diferencaSabadoOuDomingo > 0) {
            return new Date(daquiXDias.getTime() + diferencaSabadoOuDomingo * MILISEGUNDOS_EM_UM_DIA);
        } else {
            return daquiXDias;
        }
    }
}

So, when we run a test:

    private static DateFormat EXIBICAO = DateFormat.getDateInstance(DateFormat.FULL, Locale.getDefault());

    public static void main(String[] args) {
        Locale.setDefault(new Locale("pt-BR"));
        Date hoje = new Date();
        System.out.println("Hoje: " + EXIBICAO.format(hoje));
        for (int i = 1; i <= 15; i++) {
            System.out.println("Se agendar para daqui " + i + " dias cairá em: "
                    + EXIBICAO.format(ProximoDiaDaSemana.obterDataProximoCompromisso(new Date(), i)));
        }
    }

We have the desired result:

Today: Friday, July 10, 2015

If you schedule for 1 day you will fall in: Monday, July 13 2015

If scheduled for 2 days from now it will fall on: Monday, July 13 2015

If scheduled for 3 days from now it will fall on: Monday, July 13 2015

If you schedule for 4 days from now it will fall on: Tuesday, July 14 2015

If you schedule for 5 days you will fall on: Wednesday, July 15 2015

If scheduled for 6 days from now it will fall on: Thursday, July 16 2015

If scheduled for 7 days from now it will fall on: Friday, July 17 2015

If scheduled for 8 days from now it will fall on: Monday, July 20 2015

If scheduled for 9 days from now it will fall on: Monday, July 20 2015

If scheduled for 10 days from now it will fall on: Monday, July 20 2015

If scheduled for 11 days from now it will fall on: Tuesday, July 21 2015

If scheduled for 12 days from now it will fall on: Wednesday, July 22nd 2015

If scheduled for 13 days from now it will fall on: Thursday, July 23rd 2015

If you schedule for 14 days from now it will fall on: Friday, July 24th 2015

If scheduled for 15 days from now it will fall on: Monday, July 27th 2015