java得到某年某周的第一天实现思路及代码

直接上代码
复制代码 代码如下:
import java.util.Calendar;
import java.util.Date;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class DateUtils {

private static final Log log = LogFactory.getLog(DateUtils.class);

public static int getWeekOfYear(Date date) {
Calendar c = Calendar.getInstance();
c.setFirstDayOfWeek(Calendar.MONDAY);

c.setMinimalDaysInFirstWeek(1);
c.setTime(date);
return c.get(Calendar.WEEK_OF_YEAR);
}

public static int getMaxWeekNumOfYear(int year) {
Calendar c = Calendar.getInstance();
c.set(year, Calendar.DECEMBER, 31, 23, 59, 59);
return getWeekOfYear(c.getTime());
}

public static Date getFirstDayOfWeek(int year, int week) {
Calendar c = Calendar.getInstance();
c.set(Calendar.YEAR, year);
c.set(Calendar.WEEK_OF_YEAR, week);
c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);//设置周一
c.setFirstDayOfWeek(Calendar.MONDAY);
return c.getTime();
}


public static Date getLastDayOfWeek(int year, int week) {
Calendar c = Calendar.getInstance();
c.set(Calendar.YEAR, year);
c.set(Calendar.WEEK_OF_YEAR, week);
c.setFirstDayOfWeek(Calendar.MONDAY);
c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek() + 6); // Sunday

return c.getTime();
}


public static Date getFirstDayOfMonth(int year, int month) {
Calendar c = Calendar.getInstance();
c.set(Calendar.YEAR, year);
c.set(Calendar.MONTH, month-1);
c.set(Calendar.DAY_OF_MONTH, c.getActualMinimum(Calendar.DAY_OF_MONTH));
return c.getTime();
}


public static Date getLastDayOfMonth(int year, int month) {
Calendar c = Calendar.getInstance();
c.set(Calendar.YEAR, year);
c.set(Calendar.MONTH, month-1);
c.set(Calendar.DAY_OF_MONTH, c.getActualMaximum(Calendar.DAY_OF_MONTH));
return c.getTime();
}

public static Date getFirstDayOfQuarter(int year, int quarter) {
int month = 0;
if (quarter > 4) {
return null;
} else {
month = (quarter - 1) * 3 + 1;
}
return getFirstDayOfMonth(year, month);
}

public static Date getLastDayOfQuarter(int year, int quarter) {
int month = 0;
if (quarter > 4) {
return null;
} else {
month = quarter * 3;
}
return getLastDayOfMonth(year, month);
}

public static Date getFirstDayOfYear(int year) {
return getFirstDayOfQuarter(year,1);
}


public static Date getLastDayOfYear(int year) {
return getLastDayOfQuarter(year,4);
}

public static void main(String[] args) {
log.info(getFirstDayOfWeek(2013,1));
log.info(getLastDayOfWeek(2013,1));

log.info(getFirstDayOfMonth(2013,2));
log.info(getLastDayOfMonth(2013,2));

log.info(getFirstDayOfQuarter(2013,2));
log.info(getLastDayOfQuarter(2013,2));

log.info(getFirstDayOfYear(2013));
log.info(getLastDayOfYear(2013));

}
}