Why does LongSummaryStatistics implement IntConsumer?

Question

Why does LongSummaryStatistics implement IntConsumer when there is IntSummaryStatistics which also implements IntConsumer?

Answer 1

LongSummaryStatistics implements IntConsumer in order that it can accept int values as well as long values.

For example, this allows you to pass it to a method requiring an IntConsumer in order to consume some int data abstractly:

LongSummaryStatistics lss = new LongSummaryStatistics();
someMethod(lss);

void someMethod(IntConsumer consumer) { ... }

There's no real reason why a LongSummaryStatistics shouldn't be usable for this purpose: int can always be widened to long without loss. However, the type system wouldn't allow lss to be used as a parameter to someMethod unless LongSummaryStatistics implemented IntConsumer directly.

True, you could do this without implementing the interface, using a lambda:

someMethod(i -> lss.consume(i));

but it's just a bit neater to use the reference directly.