use-retrolambda.md

Use Retrolambda

Retrolambda enables lambda expressions and method references on Android by transforming Java 8 bytecode to bytecode for Java 7 and lower. While this may sound scary, lambda expressions and method references remove the syntactic boilerplate from the anonymous classes you must define when providing Func and Action implementations, thereby greatly improving your code's readability. Additionally, the Gradle plugin makes integrating Retrolambda with your build seamless.

Without Retrolambda, your RxJava code will look like:

mContentDatabase
    .fetchContentItems(ImmutableSet.of(contentItemId))
    .map(new Func1<Map<ContentItemIdentifier, ContentItem>, ContentItem>() {
        @Override
        public ContentItem call(final Map<ContentItemIdentifier, ContentItem> resultSet) {
            return checkNotNull(resultSet.get(contentItemId));
        }
    })
    .map(new Func1<ContentItem, TopicPath>() {
        @Override
        public TopicPath call(final ContentItem contentItem) {
            return contentItem.topicPath();
        }
    })
    .subscribe(new Action1<TopicPath>() {
        @Override
        public void call(final TopicPath topicPath) {
            openContentViewActivity(contentItemId, topicPath);
        }
    });

With Retrolambda, your RxJava code will look like:

mContentDatabase
    .fetchContentItems(ImmutableSet.of(contentItemId))
    .map(resultSet -> checkNotNull(resultSet.get(contentItemId)))
    .map(ContentItem::topicPath)
    .subscribe(topicPath -> {
        openContentViewActivity(contentItemId, topicPath);
    });

We at Khan Academy have been using it in our Android application with no issues. Many other companies use it with their own applications. Use it with your own application if you are using RxJava.