Get the end of a month

import java.util.Calendar;
import java.util.Date;

public class Main {
  public static void main(String[] argv) {
    System.out.println(getEndOfMonth(new Date()));
  }

  public static Date getEndOfMonth(Date day) {
    return getEndOfMonth(day, Calendar.getInstance());
  }

  public static Date getEndOfMonth(Date day, Calendar cal) {
    if (day == null)
      day = new Date();
    cal.setTime(day);

    // set time to end of day
    cal.set(Calendar.HOUR_OF_DAY, cal.getMaximum(Calendar.HOUR_OF_DAY));
    cal.set(Calendar.MINUTE, cal.getMaximum(Calendar.MINUTE));
    cal.set(Calendar.SECOND, cal.getMaximum(Calendar.SECOND));
    cal.set(Calendar.MILLISECOND, cal.getMaximum(Calendar.MILLISECOND));

    // set time to first day of month
    cal.set(Calendar.DAY_OF_MONTH, 1);

    // add one month
    cal.add(Calendar.MONTH, 1);

    // back up one day
    cal.add(Calendar.DAY_OF_MONTH, -1);

    return cal.getTime();
  }
}