java 实现当前时间的前几周和当前时间的前几个月

这个方法就是统计前几周或前几月：durationType： 是周统计，还是月统计 ，durationNumber ：当前日期的前几个。比如说3就是

19-06-2011--25-06-2011，12-06-2011--18-06-2011，05-06-2011--11-06-2011 是整个周

同理月也是01-05-2011-31-05-2011 等

public static List<String> getDateStringList(final Calendar cal, final String durationType, final int durationNumber) {

final List<String> dateList = new ArrayList<String>();

final SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");

if ("WEEK".endsWith(durationType) && durationNumber > 0) {

final int dayOfWeek = cal.get(Calendar.DAY_OF_WEEK);

cal.add(Calendar.DATE, -dayOfWeek);

final String dateStrEndFirstWeek = sdf.format(cal.getTime());

cal.add(Calendar.DATE, -6);

final String dateStrStartFirstWeek = sdf.format(cal.getTime());

final String dateStrFristWeek = dateStrStartFirstWeek + " - " + dateStrEndFirstWeek;

dateList.add(dateStrFristWeek);

for (int i = 0; i < durationNumber - 1; i++) {

cal.add(Calendar.DATE, -1);

final String dateStrEnd = sdf.format(cal.getTime());

cal.add(Calendar.DATE, -6);

final String dateStrStart = sdf.format(cal.getTime());

final String dateStr = dateStrStart + " - " + dateStrEnd;

dateList.add(dateStr);

}

return dateList;

} else if ("MONTH".endsWith(durationType) && durationNumber > 0) {

for (int i = 0; i < durationNumber; i++) {

cal.set(Calendar.DATE, 1);

cal.add(Calendar.MONTH, -1);

final String dateStrStart = sdf.format(cal.getTime());

cal.roll(Calendar.DATE, -1);

final String dateStrEnd = sdf.format(cal.getTime());

final String dateStr = dateStrStart + " - " + dateStrEnd;

dateList.add(dateStr);

}

return dateList;

}

return null;

}