Presented as part of the JetBrains India & Core Java meetup in Thermo Fisher Scientific on 29th Feb. Has videos - so may code examples not display well in this presentation.

1. Automated Refactoring
in IntelliJ IDEA
Ganesh Samarthyam

2. You can use IntelliJ IDEA
for some amazing stuff!

4. Refactoring is just a
fancy term for
improving the existing
code

5. What you see can be
misleading!

6. Simple code improvements
Optimize imports

8. Auto reformat
Clean-up formatting mess automatically

10. Auto improve
Generate code to improve code
(e.g., exception safety with try-catch-finally)

12. Renaming variables
Save pain in manually finding and replacing variables

14. Moving classes
Classes in their rightful place (i.e., their own files)

16. Auto-simplify code
Automatically simplify complex constructs to simpler ones!

18. Automated code refactoring
Extracting methods
Extracting constants
Extracting fields

22. How programming is transformed
with automated improvements
Extract fields
Extract constants
Surround with try-catch blocks
Merge try-catch blocks
Extract methods

24. Extracting method
references

26. Or choose a better
refactoring!

28. Automated design
refactoring

29. Extracting “Parameter
Objects”
Refactor “data clumps” by refactoring to abstractions

31. Design smell
class Device {
private UUID deviceId;
private String name;
private boolean status;
private LocalDateTime startDateTime;
private double generatedPower;
public Device(UUID deviceId, String name, boolean status,
LocalDateTime startDateTime, double generatedPower) {
this.deviceId = deviceId;
this.name = name;
this.status = status;
this.startDateTime = startDateTime;
this.generatedPower = generatedPower;
}
@Override
public String toString() {
return "Device{" +
"deviceId=" + deviceId +
", name='" + name + ''' +
", status=" + status +
", startDateTime=" + startDateTime +
", generatedPower=" + generatedPower +
'}';
}
}

32. Long constructor parameter
list smell
var device = new Device(UUID.randomUUID(), "FSF11", false, LocalDateTime.now(), 0);

35. Refactoring to Builder pattern
import java.time.LocalDateTime;
import java.util.UUID;
public class DeviceBuilder {
private UUID deviceId;
private String name;
private boolean status;
private LocalDateTime startDateTime;
private double generatedPower;
public DeviceBuilder setDeviceId(UUID deviceId) {
this.deviceId = deviceId;
return this;
}
public DeviceBuilder setName(String name) {
this.name = name;
return this;
}
public DeviceBuilder setStatus(boolean status) {
this.status = status;
return this;
}
public DeviceBuilder setStartDateTime(LocalDateTime startDateTime) {
this.startDateTime = startDateTime;
return this;
}
public DeviceBuilder setGeneratedPower(double generatedPower) {
this.generatedPower = generatedPower;
return this;
}
public Device createDevice() {
return new Device(deviceId, name, status, startDateTime, generatedPower);
}
}

36. Refactoring to Builder pattern
var device = new DeviceBuilder().setDeviceId(UUID.randomUUID())
.setName("FSF11")
.setStatus(false)
.setStartDateTime(LocalDateTime.now())
.setGeneratedPower(0)
.createDevice();
var device = new Device(UUID.randomUUID(), "FSF11", false, LocalDateTime.now(), 0);

37. Auto refactor to functional
programming!
Key idea is to use internal iteration (e.g., forEach)
instead of external iteration (e.g., for loops)
Another key idea is to use stream API
instead of “hand-coding” loops

38. External to internal iteration
List<String> strings = Arrays.asList("eeny", "meeny", "miny", "mo");
strings.forEach(string -> System.out.println(string));
List<String> strings = Arrays.asList("eeny", "meeny", "miny", "mo");
for(String string : strings) {
System.out.println(string);
}

41. This refactoring is manual!
public static void main(String []file) throws Exception {
// process each file passed as argument
// try opening the file with FileReader
try (FileReader inputFile = new FileReader(file[0])) {
int ch = 0;
while( (ch = inputFile.read()) != -1) {
// ch is of type int - convert it back to char
System.out.print( (char)ch );
}
}
// try-with-resources will automatically release FileReader object
}
public static void main(String []file) throws Exception {
Files.lines(Paths.get(file[0])).forEach(System.out::println);
}

42. There are some things money can't buy.
For everything else, there's MasterCard!

43. There are some things you have to hand-code.
For everything else, there's IntelliJ!