Kotlin is a statically-typed programming language designed for the Java Virtual Machine (JVM) by JetBrains. One of Kotlin's standout features is its null safety, which helps developers avoid the dreaded null pointer exceptions commonly found in many programming languages.
In Kotlin, null is not a valid value for most variables by default. To allow null values, we must explicitly declare a variable as nullable using the nullable type modifier "?". This forces developers to handle null references at compile-time, reducing the likelihood of runtime crashes due to null pointer exceptions.
Safe calls in Kotlin allow us to safely access properties and call methods on nullable objects without risking a null pointer exception. Using the safe call operator "?." after a nullable variable ensures that the expression is only evaluated if the variable is not null. If the variable is null, the expression returns null instead of throwing an exception.
Let's consider the following example where we have a nullable variable name
of type String?
:
val name: String? = "John Doe"
val length = name?.length
In the above code snippet, the safe call operator "?." ensures that the length
property is only accessed if name
is not null. If name
is null, the length
variable will also be null.
The Elvis operator, denoted by "?:", provides an alternative value to be used when the expression preceding it is null. The Elvis operator comes in handy when assigning a default value to a nullable variable if the original value is null.
Let's modify our previous example to include the Elvis operator:
val name: String? = null
val length = name?.length ?: 0
In the above code, if name
is null, the Elvis operator assigns a default value of 0 to length
. This ensures that length
is always assigned a non-null value, avoiding any potential null pointer exceptions.
Kotlin's null safety features, such as safe calls and the Elvis operator, provide a more robust and safer programming experience. By enforcing null checks at compile-time, Kotlin helps developers write code that is less prone to null pointer exceptions, leading to more reliable and resilient applications.