cached data provider

dp2.java

interface DataProvider<I, R> {
    T calculate(I input);
}

@RequiredArgsConstructor
public class DataProviderCached<I, R> implements DataProvider<I, R> {
    private final DataProvider delegate;
    private final Map<I, R> cache = new ConcurrentHashMap<>();

    @Override
    public R calculate(I input) {
        return cache.computeIfAbsent(input, delegate::calculate);
    }
}