Calendar 获取本周周一、周五时间，以及获取当月第一天

package common.util;

import java.text.SimpleDateFormat;

import java.util.Calendar;

import java.util.Date;

import java.util.GregorianCalendar;

public class WorkDay {
/**
* 得到本周周一日期
* @return
*/
public static String getWeekMonday(){
SimpleDateFormat formater=new SimpleDateFormat("MM/dd/yyyy");
Calendar cal=new GregorianCalendar();
cal.setFirstDayOfWeek(Calendar.MONDAY);
cal.setTime(new Date());
cal.set(Calendar.DAY_OF_WEEK, cal.getFirstDayOfWeek());
Date first=cal.getTime();
return formater.format(first);
}
/**
* 得到本周周五日期
* @return
*/
public static String getWeekFriday(){
SimpleDateFormat formater=new SimpleDateFormat("MM/dd/yyyy");
Calendar cal=new GregorianCalendar();

        cal.setFirstDayOfWeek(Calendar.MONDAY);

        cal.set(Calendar.DAY_OF_WEEK, cal.getFirstDayOfWeek() + 4);

        Date last=cal.getTime();

        return  formater.format(last);
}
/**
* 获取当月第一天
* @return
*/
public static String getMonthFirstday(){
SimpleDateFormat formater=new SimpleDateFormat("MM/dd/yyyy");
Calendar c = Calendar.getInstance();    

         c.add(Calendar.MONTH, 0);

         c.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天 

         String first = formater.format(c.getTime());
    return first;
}

}