Java 8 Streams : simplifying o1 – Objects. equals(o1.getSome().getSomeOther(), o2.getSome().getSomeOther()) in the stream

Given the following code:

stream.filter(o1 -> Objects.equals(o1.getSome().getSomeOther(),
                                   o2.getSome().getSomeOther())

How can this be simplified?

Are there some equals-utilities that let you extract a key first, like Comparator.comparing Same as Which accepts the key extractor function?

Note that the code itself (getSome().

getSomeOther()) is actually generated from the pattern.

Edit: (After discussing and revisiting with colleagues: Is there a convenience method to create a Predicate that tests if a field equals a given value?)

We now have the following reusable functional interface:

@FunctionalInterface
public interface Property<T, P> {

P extract(T object);

default Predicate<T> like(T example) {
     Predicate<P> equality = Predicate.isEqual(extract(example));
     return (value) -> equality.test(extract(value));
  }
}

and the following static convenience method:

static <T, P> Property<T, P> property(Property<T, P> property) {
  return property;
}

Filtering now looks like:

stream.filter(property(t -> t.getSome().getSomeOther()).like(o2))

What I like about this solution compared to the previous solution: it clearly separates the extraction of properties from the creation of Predicate itself, and speaks more clearly about what is happening.

Previous solution:

<T, U> Predicate<T> isEqual(T other, Function<T, U> keyExtractFunction) {
  U otherKey = keyExtractFunction.apply(other);
  return t -> Objects.equals(keyExtractFunction.apply(t), otherKey);
}

This results in the following usage:

stream.filter(isEqual(o2, t -> t.getSome().getSomeOther())

But I’d be happier if someone had a better solution.