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javavariablesmethodsconstructorfinal

How to initialise a final variable that requires complex computation?

I'm a beginner at Java. I was wondering, what to do in situations where a variable requires complex computation before being initialised, but once initialised, it will not change. I wanted to make the variable final, but instead of initialising it in constructor, I would rather initialise it in a method so this method can be reused later. Is there any way to achieve this?

In addition to all the requirements above, what happen if I want to compute the value of this variable only when I need it (because its computationally expensive to calculate it). What should I do in situations like this?

Solution

  • You can try the memoize supplier from Guava:

    Supplier<T> something = Suppliers.memoize(new Supplier<T>() {
    // heavy computation
    return result.
});

something.get();
something.get(); // second call will return the memoized object.