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# Kotlin Null safety


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## Nullable և Non-Null հղումներ

**Nullable**
```kotlin
var nullableText: String? = "abc"
nullableText = null
```

**Non-Null**
```kotlin
var nonNullText: String = "abc"
nonNullText = null // կոմպիլյացիայի սխալ
```

```kotlin
var nonNullText: String = "abc"
nonNullText = nullableText // կոմպիլյացիայի սխալ
```


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## Smart casts

```kotlin
val x = readln().toIntOrNull()
val y = readln().toIntOrNull()

if (x != null && y != null) {
    // x: String? -> x: String
    // y: String? -> y: String
    println(x * y)
}
else {
    println("'x' or 'y' is not a number")
}
```

...


---


...

```kotlin
val x = readln().toIntOrNull()
val y = readln().toIntOrNull()

if (x == null || y == null) {
    println("'x' or 'y' is not a number")
    return
}
// x: String? -> x: String
// y: String? -> y: String

println(x * y)
```


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