Oleh Dovhai, Java developer, tells about Guava features and shows how it works. Presentation includes: -basic overview of Guava collections and utils; -some practical examples; -comparison of code and execution time with other utils. Exampler can be found here: http://goo.gl/x4XJfi

1. make your code easier and faster

2. New data structures
● Multimap: one key - several values
○ HashMultimap - does not allow duplicating key-value pairs
○ LinkedListMultimap - traversal in order of adding
○ TreeMultimap - sorted Multimap

3. Multimap before
1. Map<Employee, List<Role>> map = new HashMap<Employee, List<Role>>();
2. public void grant(Employee employee, Role role) {
3. List<Role> roles = map.get(employee);
4. if (roles == null) {
5. roles = new ArrayList<Role>();
6. map.put(employee, roles);
7. }
8. roles.add(role);
9. }

4. Multimap after
1. Multimap<Employee, Role> multimap = ArrayListMultimap.create();
2. public void grant(Employee employee, Role role) {
3. multimap.put(employee, role);
4. }

5. BiMap
● Bidirectional map - values can be used as keys.
1. BiMap<String, Integer> bimap = HashBiMap.create();
2. bimap.put("ONE", 1);
3. bimap.put("TWO", 2);
4. BiMap<Integer, String> inversed = bimap.inverse();

6. Multiset
● allows adding duplicates
● stores the number of duplicates
● HashMultiset, LinkedHashMultiset, TreeMultiset, ConcurrentHashMultiset
1. Multiset<String> tags = HashMultiset.create();
2. for (BlogPost post : getAllBlogPosts()) {
3. tags.addAll(post.getTags());
4. }
5. tags.elementSet();
6. tags.count("habr");

7. Immutable collections
● ImmutableList, ImmutableSet, ImmutableMap etc.
ImmutableSet<Integer> LUCKY_NUMBERS =
ImmutableSet.of(4, 8, 15, 16, 23, 42);
ImmutableMap<Integer, String> numberNames =
ImmutableMap.of(1, "ONE", 2, "TWO", 3, "THREE");
//max 5 elements by .of

8. ImmutableMap builder
1. Map<Integer, String> numberNamesExtended =
2. ImmutableMap.<Integer, String>builder()()
3. .putAll(numberNames)
4. .put(5, "FIVE")
5. .put(6, "SIX")
6. .build();

9. Utils
● Lists, Sets, Map, Strings
● Iterables, FluentIterable, Optional
● Predicate, Function
● Ordering, Range
Lets practice

10. Articles
● http://docs.guava-libraries.googlecode.
com/git/javadoc/index.html?overview-summary.html
● http://java.dzone.com/articles/google-guava-cleaner-code
● http://habrahabr.ru/post/91215