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1. https://kotlinlang.org/docs/reference/idioms.html#string-interpolation

   Code Block
   println("Name $name")

   
   

2. Prefer read-only `val` over mutable `var`
   

   Code Block
   /* bad */ var counter = 0 for(i in 0..20){ counter += i } /* preferred */ val sum = (0..20).sum()

   
   

3. Unit as a return type

   Code Block
   fun doSomething(): Unit{ println("do something") }

   
   

4. https://kotlinlang.org/docs/reference/idioms.html#single-expression-functions

   Code Block
   fun theAnswer() = 42

   
   

5. https://kotlinlang.org/docs/reference/idioms.html#default-values-for-function-parameters

   Code Block
   fun foo(a: Int = 0, b: String = "") { ... }

   
   

6. https://kotlinlang.org/docs/reference/idioms.html#creating-a-singleton

   Code Block
   object Resource { val name = "Name" }

   
   

7. https://kotlinlang.org/docs/reference/idioms.html#instance-checks

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   when (x) { is Foo -> ... is Bar -> ... else -> ... }

   
   

8. https://kotlinlang.org/docs/reference/idioms.html#creating-dtos-pojospocos
   

   Code Block
   data class Customer(val name: String, val email: String)

   
   

9. Use the fact that `return` and `throw` have type `Nothing`, https://kotlinlang.org/docs/reference/idioms.html#todo-marking-code-as-incomplete

   Code Block
   val x = foo() ?: return notFound() val y = if(conditionSatisfied()){ 1.0 } else { error("Condition is not satisfied"}//throws inside, the type is Nothing }

   
   

10. Nullable truth.

    Code Block
    a?.b == true //instead of a?.b ?: false

    
    

11. Safe chain and elvis (https://kotlinlang.org/docs/reference/idioms.html#if-not-null-and-else-shorthand)
    

    Code Block
    val files = File("Test").listFiles() println(files?.size ?: "empty")

    
    

12. https://kotlinlang.org/docs/reference/idioms.html#execute-if-not-null

    Code Block
    val value = ... value?.let { ... // execute this block if not null }

    
    

13. https://kotlinlang.org/docs/reference/idioms.html#extension-functions

    Code Block
    fun String.spaceToCamelCase() { ... } "Convert this to camelcase".spaceToCamelCase()

    
    

14. Extension properties

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    import java.util.Calendar var Calendar.year get() = get(Calendar.YEAR) set(value) = set(Calendar.YEAR, value) val calendar = Calendar.getInstance() println(calendar.year) // 2020 calendar.year = 2021 println(calendar.year) // 2021

    
    

15.  With block

• Companion object

https://kotlinlang.org/docs/reference/idioms.html#checking-element-presence-in-a-collection

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