Melhorando a produtividade com Kotlin

Recentemente, escrevi um artigo sobre o que há de novo no Kotlin 1.4.20. E o primeiro comentário acabou sendo um pouco injusto com Kotlin.

Ele argumentou que por que o Kotlin deveria estar no desenvolvimento móvel, porque existe o Java, porque é uma das melhores linguagens de programação.

E para tudo isso, muito código do Android Framework é escrito em Java, ou melhor, mais de 50%!

Antes de dar minha opinião e contar essa história, por favor, não me bata com cadeiras.

Bem, vamos começar com estatísticas!

O que dizem os desenvolvedores profissionais?

Google , Kotlin.

:

67 % Android , Kotlin, , !

Florina Muntenescu (Android Developer Advocate)

, Kotlin, 100% .

, .

Google , ?

Android Kotlin:

1. - , .

   
   
   
   
   

2. - Kotlin Java

   
   
   
   
   

Flipkart:

, 50% , , Kotlin.

Cash App:

Cash App Kotlin, Builder - , ( 25% ).

Kotlin Zomato

Duolingo

Duolingo - Google Play ( 100 . ).

46% ( , ..). Kotlin.

. : , , 2 !

, , !

: Java Kotlin 30%, 90%!

Kotlin

Android Java, :

1)

2) Build

Kotlin , .

Builder Java:

public class Task {
     private final String name;
     private final Date deadline;
     private final TaskPriority priority;
     private final boolean completed;

     private Task(String name, Date deadline, TaskPriority priority, boolean completed) {
         this.name = name;
         this.deadline = deadline;
         this.priority = priority;
         this.completed = completed;
     }

     public static class Builder {
         private final String name;
         private Date deadline;
         private TaskPriority priority;
         private boolean completed;

         public Builder(String name) {
             this.name = name;
         }

         public Builder setDeadline(Date deadline) {
             this.deadline = deadline;
         return this;
         }

         public Builder setPriority(TaskPriority priority) {
             this.priority = priority;
             return this;
         }

         public Builder setCompleted(boolean completed) {
             this.completed = completed;
             return this;
         }

         public Task build() {
             return new Task(name, deadline, priority, completed);
         }
     }
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

Kotlin ( hashCode(),



equals()



):

data class Task(
     val name: String,
     val deadline: Date = DEFAULT_DEADLINE,
     val priority: TaskPriority = TaskPriority.LOW,
     val completed: Boolean = false
)
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

!

Singleton Java:

public class Singleton{
    private static volatile Singleton INSTANCE;
    private Singleton(){}
    public static Singleton getInstance(){
        if (INSTANCE == null) {                // Single Checked
            synchronized (Singleton.class) {
                if (INSTANCE == null) {        // Double checked
                    INSTANCE = new Singleton();
                }
            }
        }
        return INSTANCE;
    }
    private int count = 0;
    public int count(){ return count++; }
 }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

Kotlin:

object Singleton {
     private var count = 0
     fun count(): Int {
         return count++
     }
 }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

.

Kotlin , , :

fun borrow(){
    library -= book //  operator overloading
    val (title, author) = book //  data 
    println("Borrowed $title") //  
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, Kotlin null :

var str: String? = null // , , 
												//  str    null
        
println(str?.length) //    Safe (?) 
    
val len = str?.length ?: 0 //  0,  str   null

var listOf: List<String>? = null //    null

listOf?.filter { it.length > 3 } //   
    	?.map { it.length }
      ?.forEach { println("Length more 3 -> $it") }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

Android Kotlin, , :

@Inject
lateinit var viewModelFactory: MyViewModelFactory

private val viewModel by viewModels<MyViewModel> { viewModelFactory }

      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

Kotlin , :

dependencies {
  	implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.2.0'
  	implementation "androidx.room:room-ktx:$room_version"
		implementation "androidx.paging:paging-runtime-ktx:$paging_version"
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

Java , , Kotlin 95% , Java .

, Java , :)

Kotlin , Android Framework Java Java.

:

1. Medium Florina Muntenescu (Android Developer Advocate)

   
   
   
   
   

2. Twitter Florina Muntenescu

   
   
   
   
   

3. Twitter Android Developers

   
   
   
   
   

4. Duolingo Kotlin

   
   
   
   
   

5. Android Developers Store: Zomato Kotlin