1. Google

2. Guava
Alex

3. Korotkikh
@alexkorotkikh

5. Cleaner

6. code

7. Objects:

8. hashcode
Before:
public int hashCode() {
int result = super.hashCode();
result = 31 * result + (amount != null ? amount.hashcode() : 0);
result = 31 * result + (uuid != null ? uuid.hashcode() : 0);
result = 31 * result + (channel != null ? channel.hashcode() : 0);
result = 31 * result + (type != null ? type.hashcode() : 0);
return result;
}

9. Objects:

10. hashcode
Before:
public int hashCode() {
int result = super.hashCode();
result = 31 * result + (amount != null ? amount.hashcode() : 0);
result = 31 * result + (uuid != null ? uuid.hashcode() : 0);
result = 31 * result + (channel != null ? channel.hashcode() : 0);
result = 31 * result + (type != null ? type.hashcode() : 0);
return result;
}
After:
public int hashCode() {
return Objects.hashCode(amount, uuid, channel, type);
}

11. Preconditions:

12. example
Before:
public Period(Date start, Date end) {
if (start.after(end)) {
throw new IllegralArgumentException(Start cannot be after end);
}
this.start = start;
this.end = end;
}

13. Preconditions:

14. example
Before:
public Period(Date start, Date end) {
if (start.after(end)) {
throw new IllegralArgumentException(Start cannot be after end);
}
this.start = start;
this.end = end;
}
After:
public Public(Date start, Date end) {
checkArguments(start.after(end), Start cannot be after end);
this.start = start;
this.end = end;
}

15. Preconditions:

16. example

17. II
Before:
public Period(Date start, Date end) {
if (start == null || end == null) {
throw new NullPointerException(Dates cannot be null);
}
if (start.after(end)) {
throw new IllegralArgumentException(Start can’t be after end);
}
this.start = start;
this.end = end;
}

18. Preconditions:

19. example

20. II
Before:
public Period(Date start, Date end) {
if (start == null || end == null) {
throw new NullPointerException(Dates cannot be null);
}
if (start.after(end)) {
throw new IllegralArgumentException(Start can’t be after end);
}
this.start = start;
this.end = end;
}
After:
public Period(Date start, Date end) {
this.start = checkNotNull(start, Start cannot be null);
this.end = checkNotNull(end, End cannot be null);
checkArgument(start.after(end), Start cannot be after end);
}

21. Preconditions:

22. list
•checkNotNull

23. (NullPointerException)
•checkArgument

24. (IllegalArgumentException)
•checkState

25. (IllegalStateException)
•checkElementIndex

26. (IndexOutOfBoundsException)
•etc

27. Collections:

28. creation
Before:
ListSomeJavaObject list = new ArrayListSomeJavaObject();
list.add(firstObj);
list.add(secondObj);

29. Collections:

30. creation
Before:
ListSomeJavaObject list = new ArrayListSomeJavaObject();
list.add(firstObj);
list.add(secondObj);
After:
ListSomeJavaObject list = newArrayList(firstObj, secondObj);

31. New

32. collections

33. Collections:

34. BiMap
BiMapString, String biMap = HashBiMap.create();
biMap.put(google, guava);
biMap.put(apache, commons);
assertEquals(guava, biMap.get(google));
assertEquals(google,
biMap.inverse().get(guava));

35. Collections:

36. Multimap
Before:
MapString, ListString map = new HashMapString, ListString();
if (map.get(key) == null) {
map.get(key) = new ArrayListString();
}
map.get(key).add(value);

37. Collections:

38. Multimap
Before:
MapString, ListString map = new HashMapString, ListString();
if (map.get(key) == null) {
map.get(key) = new ArrayListString();
}
map.get(key).add(value);
After:
MultimapString, String map = HashMultimap.create();
map.put(key, value);
assertTrue(map.get(key) instanceof Collection);

39. Collections:

40. immutables
Before:
ListString strings = newArrayList(“a”, “b”, “c”);
ListString unmodifiableStrings = Collections.unmodifiableList(strings);
strings.add(“d”);
assertEquals(4, unmodifiableStrings());

41. Collections:

42. immutables
Before:
ListString strings = newArrayList(“a”, “b”, “c”);
ListString unmodifiableStrings = Collections.unmodifiableList(strings);
strings.add(“d”);
assertEquals(4, unmodifiableStrings());
After:
@Test(expected = UnsupportedOperationException.class)
public void immutableList_addItem_throwException() {
ListInteger ints = ImmutableList.of(1, 2, 3);
ints.add(4)
}

43. Helper

44. utils

45. Utils:

46. Splitter
Before:
CollectionString strings = newArrayList();
for (String s : abc,def,,gh, ijk .split(,)) {
if (!s.isEmpty()) {
strings.add(s.trim());
}
}

47. Utils:

48. Splitter
Before:
CollectionString strings = newArrayList();
for (String s : abc,def,,gh, ijk .split(,)) {
if (!s.isEmpty()) {
strings.add(s.trim());
}
}
After:
IterableString strings = Splitter.on(,)
.omitEmptyStrings()
.trimResults()
.split(abc,def,,gh, ijk );

49. Utils:

50. Splitter
Before:
CollectionString strings = newArrayList();
for (String s : abc,def,,gh, ijk .split(,)) {
if (!s.isEmpty()) {
strings.add(s.trim());
}
}
After:
Splitter splitter = Splitter.on(,)
.omitEmptyStrings()
.trimResults();
IterableString strings = splitter.split(abc,def,,gh, ijk );
IterableString strings2 = splitter.split(lmno,, pqrstu,vwxyz );

51. Utils:

52. Joiner
Before:
ListString strings = newArrayList(Atomicity, Consistency, Isolation,
null, Durability);
StringBuilder sb = new StringBuilder();
for (int i = 0; i strings.size(); i++) {
String s = strings.get(i);
if (s == null) {
continue;
}
sb.append(s);
if (i strings.size() - 1) {
sb.append(, );
}
}

53. Utils:

54. Joiner
Before:
ListString strings = newArrayList(Atomicity, Consistency, Isolation,
null, Durability);
StringBuilder sb = new StringBuilder();
for (int i = 0; i strings.size(); i++) {
String s = strings.get(i);
if (s == null) {
continue;
}
sb.append(s);
if (i strings.size() - 1) {
sb.append(, );
}
}
After:
String s =
Joiner.on(, )
.skipNulls()
.join (Atomicity, Consistency, Isolation, null, Durability);

55. Utils:

56. Ranges
Before:
SetInteger acceptableMarks = newHashSet();
for (int i = 60; i = 100; i++) {
acceptableMarks.add(i);
}
boolean examPassed = acceptableMarks.contains(mark);

57. Utils:

58. Ranges
Before:
SetInteger acceptableMarks = newHashSet();
for (int i = 60; i = 100; i++) {
acceptableMarks.add(i);
}
boolean examPassed = acceptableMarks.contains(mark);
After:
RangeInteger acceptableMarks = Ranges.closed(60, 100); // [60, 100]
boolean examPassed = acceptableMarks.contains(mark);

59. Just

60. use

61. it
dependency
groupIdcom.google.guava/groupId
artifactIdguava/artifactId
version12.0/version
/dependency

62. Tnx!
Alex

63. Korotkikh
@alexkorotkikh