Avoided Defects

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Equality

see Equality before reading

// Java

int employeeAge = employee.getAge();
int supervisorAge = supervisor.getAge();
if (employeeAge == supervisorAge) // works

Integer employeeAge = employee.getAge();
Integer supervisorAge = supervisor.getAge();
if (employeeAge == supervisorAge) // wont work anymore

// Kotlin
val employeeAge : Int = employee.age
val supervisorAge : Int = supervisor.age
if (employeeAge == supervisorAge) // works

val employeeAge : Int? = employee.age
val supervisorAge : Int? = supervisor.age
if (employeeAge == supervisorAge) // still works

Nullability

By default Kotlin disallows nullable types / values. This causes the developer to be more consious with there types and avoids most null pointers at compile time.

// Kotlin

var name : String = "Testificate"
name = null // compiliation error

var name2 : String? = "Testificate"
name2 = null // all good

// you can also use the elvis operator for fallbacks

name = getNullableName() ?: "No Name"