null Pointer Exception when parsing date with Simple Date format

Question

I have a problem with converting my String into date and it gives me a null pointer exception and I've tried everything.

This is how I enter my String into my database from calendarView

mCalendarView.setOnDateChangeListener(new CalendarView.OnDateChangeListener() {
        @Override
        public void onSelectedDayChange(@NonNull CalendarView calendarView, int i, int i1, int i2) {
            string = (i1 + 1) + "/" +i2 + "/" + i;
}
        });

String key = mDatabase.push().getKey();

                HashMap<String, String> dataMap = new HashMap<>();
                dataMap.put("Date", date);
                dataMap.put("Key", key);
 mDatabase.child(key).setValue(dataMap);

Then when I retrieve it from my database I format it like this

databaseReference = FirebaseDatabase.getInstance().getReference().child("Groups").child("JMHyOvgCDvdKEZuReJvdGcExEnX2").child("HomeFragment").child("FreezerItems");
        valueEventListener = new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                HashMap<String, String> value = (HashMap<String,String>) dataSnapshot.getValue();
                if (value != null){
                    String name = value.get("Name");
                    String date = value.get("Date");

                    try {
                        dateFormat = new Date();
                        dateFormat = new SimpleDateFormat("M/dd/yyyy", Locale.US).parse(date);

                    } catch (ParseException e) {
                        Log.wtf("FailedtoChangeDate", "Fail");
                    }

My problem is when I try to convert the string to M/dd/yyyy format even though the date's format in string is like this "5/30/2018"

A screen shot when I debug it

also post the value of this variable here String date = value.get("Date"); — Quick learner, May 20 '18 at 16:29
As an aside consider throwing away the long outmoded and notoriously troublesome `SimpleDateFormat` and friends, and adding [ThreeTenABP](https://github.com/JakeWharton/ThreeTenABP) to your Android project in order to use `java.time`, the modern Java date and time API. It is so much nicer to work with. — Ole V.V., May 20 '18 at 17:40
Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Ole V.V., May 20 '18 at 17:48
Please post your stacktrace (get hold of it somehow, it’s vital). — Ole V.V., May 20 '18 at 17:49

Quick learner · Accepted Answer · 2018-05-20T17:44:08.927

1

Updating my answer :-

Your date input 05/20/2018

String input_date = "05/20/2018";  
SimpleDateFormat format = new SimpleDateFormat("MM/dd/yyyy");  
try {  
    Date date = format.parse(input_date );  
    System.out.println(date);  
} catch (ParseException e) {
    e.printStackTrace();  
}

edited May 20 '18 at 17:44

answered May 20 '18 at 16:27

Quick learner

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updated this answer for 05/20/2018 date , Try it and it will work :) – Quick learner May 20 '18 at 16:54
check this value again String date = value.get("Date"); and debug your code – Quick learner May 20 '18 at 16:55
I even tried to copy how the data is entered and pasted where the data is being retrieved so no errors but still won;t work – Kristofer May 20 '18 at 16:55
is it still crashing ? – Quick learner May 20 '18 at 16:57
yea, also I'm not sure how to debug my code, Ill update my question – Kristofer May 20 '18 at 16:59
yes please do it and just how to use debugger and set check points , it will help dear :) – Quick learner May 20 '18 at 17:00
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/171428/discussion-between-kristofer-and-quick-learner). – Kristofer May 20 '18 at 17:00
While your code works, (1) it’s still using the long outdated and notoriously troublesome `SimpleDateFormat` also used in the question, (2) it doesn’t seem to give any guidance on how to solve the `NullPointerException` that the question is about. – Ole V.V. May 20 '18 at 17:51
FYI i have explained the reason for null pointer exception which is due to wrong format :) , correct me if i have posted wrong code or post your answer explaining everything – Quick learner May 20 '18 at 18:01
A wrong format would give a `ParseException`, not a `NullPointerException`. So no, you have not explained, – Ole V.V. May 21 '18 at 06:20

score 0 · Answer 2 · answered May 21 '18 at 06:18

Your screenshot is very useful. It shows that value returns null for both name and date. So the values you try to take out from this map are not in there. This is why date is null and you get your NullPointerException.

Why there is no date (and no name) in the map lies outside the code that we can see in the question, so I cannot tell.

null Pointer Exception when parsing date with Simple Date format

2 Answers2