Kotlin is a modern programming language that was created by JetBrains as a replacement for Java, with some key advantages: - It simplifies development tasks like creating data classes and working with collections. Kotlin also reduces the amount of code needed for common operations. - Kotlin works seamlessly with Java code and is fully interoperable. It is also compatible with existing Java tools and platforms. - The language has seen growing adoption since its 1.0 release in 2016 and is now officially supported by Google for Android development. Many large companies and open source projects use Kotlin due to its improvements over Java.

1. Why otlin?
Sprint Part 1

2. Kirill Rozov
Senior Android Developer
@kiryl.rozau
kiryl.rozau@apalon.com

3. Main facts
• Was born at JetBrains in 2010
• Modern replacement of Java
• Releases
• 1.0 was at February 2016
• 1.1 was at March 2017
• Kotlin is official supported by Google for Android

5. Simplify the development

6. Data Class in Java
public class Device {
private String id;
private String name;
private String cpu;
private long ramSize;
public Device(@NotNull String id, @NotNull String name, @NotNull String cpu, long ramSize) {
this.id = id;
this.name = name;
this.cpu = cpu;
this.ramSize = ramSize;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getCpu() {
return cpu;
}
public void setCpu(String cpu) {
this.cpu = cpu;
}
public long getRamSize() {
return ramSize;
}
public void setRamSize(long ramSize) {
this.ramSize = ramSize;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Device device = (Device) o;
return ramSize == device.ramSize && id.equals(device.id) && name.equals(device.name) && cpu.equals(device.cpu);
}
@Override
public int hashCode() {
int result = id.hashCode();
result = 31 * result + name.hashCode();
result = 31 * result + cpu.hashCode();
result = 31 * result + (int) (ramSize ^ (ramSize >>> 32));
return result;
}
@Override
public String toString() {
return "Device{" + "id='" + id + ''' + ", name='" + name + ''' + ", cpu='" + cpu + ''' + ", ramSize=" + ramSize + ‘}';
}
}

7. Data Class in Kotlin
data class Device(var id: String, var name: String, var cpu: String, var ramSize: Long)

8. Operations with data array
List<Device> qualcommCpuDevices = new ArrayList<>();
for (Device device : devices)
if (device.getCpu().equals("Qualcomm"))
qualcommCpuDevices.add(device);
List<Device> largeRamQualcommDevices = new ArrayList<>();
for (Device device : qualcommCpuDevices)
if (isLargeRamDevice(device))
largeRamQualcommDevices.add(device);
List<String> deviceNames = new ArrayList<>();
for (Device device : largeRamQualcommDevices)
deviceNames.add(device.getName());

9. Operations with data array
devices.stream()
.filter(device -> device.getCpu().equals("Qualcomm"))
.filter(Device::isLargeRamDevice)
.map(Device::getName)
.collect(Collectors.toList());
List<Device> qualcommCpuDevices = new ArrayList<>();
for (Device device : devices)
if (device.getCpu().equals("Qualcomm"))
qualcommCpuDevices.add(device);
List<Device> largeRamQualcommDevices = new ArrayList<>();
for (Device device : qualcommCpuDevices)
if (isLargeRamDevice(device))
largeRamQualcommDevices.add(device);
List<String> deviceNames = new ArrayList<>();
for (Device device : largeRamQualcommDevices)
deviceNames.add(device.getName());

10. Operations with data array
devices.stream()
.filter(device -> device.getCpu().equals("Qualcomm"))
.filter(Device::isLargeRamDevice)
.map(Device::getName)
.collect(Collectors.toList());
devices.filter { it.cpu == "Qualcomm" }
.filter(Device::isLargeRamDevice)
.map { it.name }
.toList()

11. Operations with data array
Characters
0
100
200
300
400
500
Java Java 8 Kotlin
97
153
447

12. Simplify the development
• Reducing the amount of code
• Integration with modern development software
• Built-in tools for improving code stability

14. Interoperability

15. Interoperability
• 100% compatibility with Java code in both directions
• No need to bundle additional runtime to the app
• Backward compatibility with previous versions
• Easy convert Java code to Kotlin

16. Support

17. Support
• Developing by JetBrains
• Google official support for Android
• Open Source
• Working with community
• Frequent updates

18. GitHub repos count
Repositories
0
2500
5000
7500
10000
2013 2014 2015 2016 2017 Now
Release 1.0
Release 1.1
Official Android support

19. Who uses Kotlin

21. Platforms

22. Platforms

23. Learning

24. Learning
• Easy “Getting Started”
• Studying Kotlin: online or offline
• Many code samples and videos
• Good documentation
• Books from language makers

25. Reduce time

26. Reduce time
1. Less time for implementation
2. More stability -> less test time
3. Interoperability with old projects
4. Low entry barrier for Java developers
5. Common codebase for different platforms

28. Next step?

29. Q&A

30. Thanks!
goo.gl/ApXkhW