Java 获取本周，本月的开始和结束日期

获取本周的周一和周日的日期：

 Calendar ca=Calendar.getInstance();
  SimpleDateFormat f=new SimpleDateFormat("yyyy-MM-dd");
  int dayOfWeek = ca.get(Calendar.DAY_OF_WEEK);
  //中国习惯：周一是一周的开始
    if (dayOfWeek==1) {
dayOfWeek=7;
}else{
dayOfWeek--;
}
//   Log.d("tag","dayofweek="+dayOfWeek+"min= "+ca.getActualMinimum(Calendar.DAY_OF_WEEK)+" max="+ca.getActualMaximum(Calendar.DAY_OF_WEEK));
  Calendar  cal=(Calendar)ca.clone();
   
  cal.add(Calendar.DATE,1-dayOfWeek);
  Date date1=cal.getTime();
  cal=(Calendar)ca.clone();
  cal.add(Calendar.DATE,7-dayOfWeek);
  Date date2=cal.getTime();
  String str1=f.format(date1);
  String str2=f.format(date2);
  Log.d("tag","date1="+str1+" date2="+str2);

获取本月一号和后一天的日期：

Calendar ca=Calendar.getInstance();
  SimpleDateFormat f=new SimpleDateFormat("yyyy-MM-dd");
  int maximum = ca.getActualMaximum(Calendar.DAY_OF_MONTH);
  int minmum=ca.getActualMinimum(Calendar.DAY_OF_MONTH);
  int day=ca.get(Calendar.DAY_OF_MONTH);
  Calendar cal=(Calendar)ca.clone();
  cal.add(Calendar.DATE, maximum-day);
  Date dateD=cal.getTime();
  String strD=f.format(dateD);
  cal=(Calendar)ca.clone();
  cal.add(Calendar.DATE, minmum-day);
  Date dateX=cal.getTime();
  String strX=f.format(dateX);
  Log.d("tag","dateD="+strD+" dateX="+strX);