How is null safety ensured in Kotlin and how is it implemented in practice?

In Kotlin, null safety is built into the type system, which distinguishes between nullable and non-nullable types.

• Types without ? cannot contain null, e.g., String.
• Types with ? can contain null, e.g., String?.

This allows the compiler to catch potential errors at compile time, preventing NullPointerException.

Practical mechanisms for working with null:

• Safe call operator ?. — calls a method or accesses a property only if the object is not null.
• Elvis operator ?: — provides a default value if the expression on the left is null.
• Not-null assertion !! — forcibly asserts that the value is not null, throwing an exception if it is.

Example:

val name: String? = null
println(name?.length) // Prints null, does not throw error
println(name ?: "Unknown") // Prints "Unknown"
// println(name!!.length) // Throws NullPointerException

Thus, Kotlin helps write safer code, minimizing null-related errors.