Java 8 collector for Guava immutable collections?

Question

I really like Java 8 streams and Guava\'s immutable collections, but I can\'t figure out how to use the two together.

For example, how do I implement a Java 8 Collec

Answer 1

For your example, you can use Guava's toImmutableMap() collector. E.g.

import static com.google.common.collect.ImmutableMap.toImmutableMap;

ImmutableMap zipCodeForName =
    people.stream()
        .collect(
            toImmutableMap(Person::getName, p -> p.getAddress().getZipCode()));

ImmutableMap personForName =
    people.stream()
        .collect(
            toImmutableMap(Person::getName, p -> p));

The top answer has the rest of the Guava immutable collectors APIs