Please, I need help

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I don't know why this doesn't work. I even tried to change comparison sign to another sides, but it still didn't help to move on. Please, tell me what i did wrong

Create a Map<String, Date> and add ten entries that represent (last name, birth date) pairs.
Remove from the map all people born in the summer.
Hint: At CodeGym, summer lasts from June 1 to August 31.

Requirements:

The program should not display text on the screen.
The program should not read values from the keyboard.
The createMap() method must create and return a HashMap that has (String, Date) elements and contains 10 entries.
The removeAllSummerPeople() method should remove from the map all people born in the summer.

package com.codegym.task.task08.task0816; import java.text.DateFormat; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; import java.util.HashMap; import java.util.Locale; import java.util.*; /* Kind Emma and the summer holidays */ public class Solution { public static HashMap<String, Date> createMap() throws ParseException { DateFormat df = new SimpleDateFormat("MMMMM d yyyy", Locale.ENGLISH); HashMap<String, Date> map = new HashMap<String, Date>(); map.put("Stallone", df.parse("JUNE 1 1980")); map.put("Petrov", df.parse("JULY 1 1980")); map.put("Siniscin", df.parse("AUGUST 1 1980")); map.put("Igorayev", df.parse("SEPTEMBER 1 1980")); map.put("Shishkov", df.parse("OCTOBER 1 1980")); map.put("Ivanov", df.parse("NOVEMBER 1 1980")); map.put("Shkurin", df.parse("DECEMBER 1 1980")); map.put("Shuckin", df.parse("JUNE 1 1980")); map.put("Pavlov", df.parse("JUNE 1 1980")); map.put("Khraponichev", df.parse("JUNE 1 1980")); return map; } public static void removeAllSummerPeople(HashMap<String, Date> map) { Calendar jun = new GregorianCalendar(Calendar.JUNE,Calendar.DAY_OF_MONTH,1); Date date1 = jun.getTime(); Calendar aug = new GregorianCalendar(Calendar.AUGUST,Calendar.DAY_OF_MONTH,31); Date date2 = aug.getTime(); for(Map.Entry<String, Date> b: map.entrySet()) { for (String s : map.keySet()) { if (b.getValue().compareTo(date1) > 0 && b.getValue().compareTo(date2) < 0) map.remove(b.getKey()); } } } public static void main(String[] args) { } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

2 June 2021, 13:49

What tests have you performed to try debugging your code?

Patrick Batterfly

Level 17 , Livny, Russian Federation

2 June 2021, 14:01

I rewrote these lines Calendar jun = new GregorianCalendar(Calendar.JUNE,Calendar.DAY_OF_MONTH,1); Calendar aug = new GregorianCalendar(Calendar.AUGUST,Calendar.DAY_OF_MONTH,31) to these ones, but that didn't really change the situation Calendar jun = new GregorianCalendar(Calendar.JUNE, Calendar.JUNE,1); Calendar aug = new GregorianCalendar(Calendar.AUGUST, Calendar.AUGUST,31);

Guadalupe Gagnon

Level 37 , Tampa, United States

2 June 2021, 14:33

Do you know what those are doing? When I say testing I mean actually observing results of the code at various points. Making changes without observing results is basically pointless. You are level 8, so don't take that as criticism, I am sure you haven't learned any debugging techniques yet. I'll share one of the easiest ways to start debugging, just simply adding println() statements into your code. So to modify that code I would simply do:

Calendar jun = new GregorianCalendar(Calendar.JUNE, Calendar.JUNE,1);
Date date1 = jun.getTime();
System.out.println(date1); // simple print line

Calendar aug = new GregorianCalendar(Calendar.AUGUST, Calendar.AUGUST,31);
Date date2 = aug.getTime();
System.out.println(date2);

Of course, this won't print anything because the main method (where code execution starts from) is empty. You are going to have to add something like this to get output

public static void main(String[] args) throws Exception{
   HashMap<String, Date> test = createMap();
   removeAllSummerPeople(test);
   System.out.println(test);
}

Those lines you shared use the GregCal constructor with 3 ints. This is defined as (Year, Month, DayOfMonth). That is setting the first date to "June 1, (year) 5" and the second one as "Aug 31, (year) 8" Your code then checks if the map contains any dates between those 2. The main problem you have with this is that by restricting the conditions to a specific year you will only be able to remove dates that are between Jun-Aug of only 1 year. Codegym will test your code with dates that have many different years and it should correctly remove any that fall between any year's dates that fall between Jun 1 and Aug 31.

Patrick Batterfly

Level 17 , Livny, Russian Federation

2 June 2021, 14:44

thanks, I got you

Guadalupe Gagnon

Level 37 , Tampa, United States

2 June 2021, 14:46

You can look up the documentation of any class in the Java docs. They are very straight forward and not a good learning resource, but when you know what information that you need they are great. In this case the GregorianCalendar constructor details: GreCal Java Docs Scroll down to "Constructor Summary" for more information. Also take a look at the "Method Summary" for the things this class can do. You should also look up the Java Docs for the Date class and the Calendar class. I will give you a hint for this task: you can call .get(Calendar.MONTH) on an object of the calendar class to get the specific month that it is (0 for January to 11 for December)

Guadalupe Gagnon

Level 37 , Tampa, United States

2 June 2021, 14:50

One last thing. You can not continue iterating over from a collection (such as a Map) after you remove an item from it. Line 39, if an item is removed on line 42 and the loop continues, will result in ConcurrentModificationException.

Patrick Batterfly

Level 17 , Livny, Russian Federation

2 June 2021, 14:53

thank you a lot. I wish you good coding