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How resolve null value in toMap

I have a problem, practically when I select two time slots within a week and generate them through a button all ok, but then when I go to delete a day of the week and then click again on the button "generate slots", I choose my week (where I had two days but now I have only one) I get the error on line 100 of code that I place there: enter image description here

Solution

  • On the shared '100' line you basically telling to JDK compiler: for each object into list create a map entry with:

    • key the value of getDay from the object
    • value the object itself

    The JDK converts it to:

    • key = object.getDay()
    • value = object

    In your list there are items which are null, example: [{obj1}, {obj2}, null, ...].

    This causes the TimeSlot::getDay to be null.getDay() in some cases. If you need to put null as key, you could transform it from TimeSlot::getDay to o -> o != null ? o.getDay() : null.

    If you do not need null as key value, you could filter them before collecting, example adding: .filter(Objects::nonNull).

    Check what-is-a-nullpointerexception-and-how-do-i-fix-it for more info.