This document provides examples of refactoring Java code to use Guava libraries and utilities. It shows code snippets before and after refactoring to use Guava's Objects, Preconditions, Collections, Splitter, Joiner, Ranges and other utilities to clean up code and make it more readable and robust. Refactoring includes using Guava to validate arguments, create immutable collections, handle nulls safely, join/split strings, and represent ranges.

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);