Question

Please show public static void main(String args[]){}

also too!

8. Given a non-empty list of dates, this method groups them based on the day of the wel on which they occurred; selects the earliest one in each group; and return the selected ones. The return is a map whose keys are the short day-of-the-week names and whose values are the selected dates. The map is sorted on its keys: public static Map latestByWeekday(List list) Example, if list is: CThu Mar 30 23:30:00 EDT 2017, Sat Dec 31 23:10:00 EST 2016, Sat Apr 01 06:00:00 EDT 2017, Thu Aug 11 00:00:00 EDT 2016, Sat Dec 31 00:15:00 EST 2016] then the return should be: Sat-Sat Dec 31 00:15:00 EST 2016, Thu=Thu Aug 11 00:00:00 EDT 2016)

Answer 1

// LatestByWeekDay.java

import java.util.Date;

import java.util.GregorianCalendar;

import java.util.Map;

import java.util.List;

import java.util.Set;

import java.util.TreeMap;

public class LatestByWeekDay {

       // method that groups a list of dates based on the day of the week and selects the earliest one in each group

       // return type is Map whose keys are the short day-of-the-week and values are the selected date

       // map is sorted on its keys

       public static Map<String,Date> latestByWeekday(List<Date> list)

       {

             Map<String,Date> result = new TreeMap<String,Date>();

             String mon;

             // loop over the list of dates

             for(int i=0;i<list.size();i++)

             {

                    mon = String.format("%ta",list.get(i)); // get the short day-of-the-week from the date

                    if(result.containsKey(mon)) // check if day is already present in map

                    {

                           // check if this date is earlier than the stored date, then replace it with this date

                           if(list.get(i).compareTo(result.get(mon)) < 0)

                                 result.put(mon, list.get(i));

                    }else // if day-of-the-week is not present, insert in Map

                           result.put(mon,list.get(i));

             }

            

             return result;

       }

public static void main(String[] args) throws IOException {

            

             // create a list of dates

             List<Date> list = new ArrayList<Date>();

             // add dates to list

             list.add(new GregorianCalendar(2017,2,30,23,30,00).getTime());

             list.add(new GregorianCalendar(2016,11,31,23,10,00).getTime());

             list.add(new GregorianCalendar(2017,3,1,6,00,00).getTime());

             list.add(new GregorianCalendar(2016,7,11,00,00,00).getTime());

             list.add(new GregorianCalendar(2016,11,31,00,15,00).getTime());

            

             // get the result

             Map<String,Date> result =latestByWeekday(list);

            

             // print the result

             Set<Map.Entry<String,Date>> resultSet= result.entrySet();

             for(Map.Entry<String, Date> entry:resultSet)

             {

                    System.out.println(entry.getKey() +" = "+entry.getValue());

             }

}

}

//end of program

Output:

Sat = Sat Dec 31 00:15:00 IST 2016 Thu = Thu Aug 11 00:00:00 IST 2016