Get the element in an arbitrarily nested JSON structure by following a path of keys (inspired by Clojure's get-in function)

getin.java

package some.package;

import com.google.gson.JsonElement;
import com.google.gson.JsonNull;

import java.util.Arrays;
import java.util.Optional;

class SomeClass {
    /**
     * Returns the element in a nested JSON structure, where keys is a "path" of
     * keys to traverse in order to retrieve the desired element.
     * If the path is empty, returns the source structure as is.
     * If the path leads to nowhere, returns empty {@link Optional<JsonElement>}.
     */
    Optional<JsonElement> getIn(JsonElement e, String... keys) {
        JsonElement v = Arrays.stream(keys).sequential()
                .reduce(e,
                        (accumulator, key) -> {
                            if (accumulator.isJsonObject()) {
                                JsonElement nested = accumulator.getAsJsonObject().get(key);
                                return nested == null ? JsonNull.INSTANCE : nested;
                            } else {
                                return JsonNull.INSTANCE;
                            }
                        },
                        (x, y) -> x // combiner will never be called since this reduction is sequential (not parallel).
                );
        return v instanceof JsonNull ? Optional.empty() : Optional.of(v);
    }
}