Java loop extracting month and year between two dates

Question

I have a ContratMercan with 2 Timestamps containing start and end dates. I have to create a new entity SeguimientoSeccion for each month between this 2 dates.

I have 2 questions:

• There is a way to improve it?
• After this I will need to manipulate the List<SeguimientoSeccion> secciones to see which one matches other entity... I though about making a Map but there can be 2 or more sections in each month and year

private List<SeguimientoSeccion> createSectionsPerMonth(ContratMercan contrato) 
{
    List<SeguimientoSeccion> secciones = new ArrayList<SeguimientoSeccion>();

    Calendar start = Calendar.getInstance();
    start.setTime(contrato.getPeriodoEntregaIni());
    start.set(Calendar.DAY_OF_MONTH, 1);

    Calendar end = Calendar.getInstance();
    end.setTime(contrato.getPeriodoEntregaFin());
    end.set(Calendar.DAY_OF_MONTH, 2);  // for loop comparison

    for (int month = start.get(Calendar.MONTH), year = start.get(Calendar.YEAR); start.before(end); month = start.get(Calendar.MONTH), year = start.get(Calendar.YEAR)) {
        SeguimientoSeccion seccion = new SeguimientoSeccion();
        seccion.setMonth(month + 1);  // natural month number
        seccion.setYear(year);

        start.add(Calendar.MONTH, 1);

        secciones.add(seccion);
    }

    return secciones;
}

Answer 1

The code would be simpler if you used a Calendar object as the loop variable.

Calendar current = …;
Calendar end = …;

for (; current.before(end); current.add(Calendar.MONTH, 1)) {
    SeguimientoSeccion seccion = new SeguimientoSeccion();
    seccion.setMonth(1 + current.get(Calendar.MONTH));  // natural month number
    seccion.setYear(current.get(Calendar.YEAR));
    secciones.add(seccion);
}

Consider implementing a SeguimientoSeccion.setMonthYear(m, y) method instead, as it's probably useless to set one of the fields without also setting the other.