How to initialise a thread-local with type Map using ThreadLocal.withInitial?

Question

I'm trying to initialise a thread-local of type Map using "ThreadLocal.withInital" method

I can proceed with setting a new ThreadLocal and adding a setter method to proceed with the initialisation. But I'm trying to find a way whether this can be done via initial.

private static final ThreadLocal<Map<Date, Boolean>> dateBooleantl = new ThreadLocal<>();

Expected Output:

private static final ThreadLocal<Map<Date, Boolean>> dateBooleantl = ThreadLocal.withInitial(<Hash-map that is set with a predefined date and a boolean>)

Answer 1

Maybe this:

private static final ThreadLocal<Map<Date, Boolean>> dateBooleantl = ThreadLocal.withInitial(() -> {
        Map<Date, Boolean> map = new HashMap<>();
        map.put(new Date(), true);
        //do other stuff...
        return map;
    });

Answer 2

ThreadLocal.withInitial method takes a Functional parameter, so it can be a Lambda, like this:

private static final ThreadLocal<Map<Date, Boolean>> dateBooleantl = ThreadLocal.withInitial(() -> {
    Map<Date, Boolean> map = new HashMap<>();
    map.put(new Date(), true);
    return map;
});