Java Utililty Methods Day of Month

Calendar calendar = new GregorianCalendar();
calendar.set(Calendar.DATE, 1);
calendar.roll(Calendar.DATE, -1);
SimpleDateFormat simpleFormate = new SimpleDateFormat("yyyy-MM-dd");
return simpleFormate.format(calendar.getTime()).trim();

SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd");
Calendar cal = Calendar.getInstance();
cal.setTime(new Date());
cal.set(Calendar.DAY_OF_MONTH, 1);
cal.add(Calendar.DAY_OF_MONTH, -1);
return format.format(cal.getTime());

Date date = new Date();
SimpleDateFormat format = new SimpleDateFormat(YYYYMMDDHHMMSS);
Calendar eCal = Calendar.getInstance();
eCal.setTime(date);
eCal.set(Calendar.DAY_OF_MONTH, 1);
eCal.add(Calendar.MONTH, 1);
eCal.add(Calendar.DATE, -1);
try {
...

Calendar c = Calendar.getInstance();
int totalday = c.getActualMaximum(Calendar.DAY_OF_MONTH);
c.set(Calendar.DAY_OF_MONTH, totalday);
System.out.println(c.getTime());
return new SimpleDateFormat("yyyy-MM-dd").format(c.getTime());

Calendar calendar = Calendar.getInstance();
calendar.setTime(new Date());
final int lastDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
Date lastDate = calendar.getTime();
lastDate.setDate(lastDay);
return sdf2.format(lastDate);

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Calendar ca = Calendar.getInstance();
ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));
String last = sdf.format(ca.getTime());
return last;

int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH) + 1;
int day = 1;
if (month > 11) {
    month = 0;
    year = year + 1;
c.set(year, month, day - 1, 0, 0, 0);
...

Calendar cal = Calendar.getInstance();
cal.setTime(currDate);
int lastDay = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
cal.set(Calendar.DAY_OF_MONTH, lastDay);
return getFormatDate(cal.getTime(), DATE_FORMAT);

Calendar calendar = Calendar.getInstance();
Date tempDate = (date == null ? new Date() : date);
calendar.setTime(tempDate);
calendar.set(Calendar.DATE, getMaxDayNum(tempDate));
calendar.set(Calendar.HOUR_OF_DAY, DEFALUT_HOUR_OF_DAY);
calendar.set(Calendar.MINUTE, DEFAULT_MINUTE);
calendar.set(Calendar.SECOND, DEFAULT_SECOND);
calendar.set(Calendar.MILLISECOND, 0);
...

date = addMonths(date, 1);
return getLastDayOfPreviousMonth(date);