In Kotlin, the `
!!` operator is called the "
not-null assertion operator," and its purpose is to assert that a value is not null. It is used when you are certain that a nullable reference is not null at a specific point in your code, and you want to communicate this assurance to the compiler. Here's an explanation of the purpose and usage of the `
!!` operator:
1. Asserting Non-Nullability : * The `
!!` operator is used to assert that a nullable reference is not null at a particular point in the code.
* It tells the compiler that you are confident the value is not null, overriding the null safety checks.
2. Nullable Types : * In Kotlin, nullable types are indicated by adding a `
?` to the type declaration.
* Nullable types allow variables to hold null values, and the compiler enforces null safety rules to prevent null pointer exceptions.
3. Potential Nullability Risks : * When using the `
!!` operator, you are explicitly telling the compiler that you are aware of the potential nullability risks and are taking responsibility for handling null values.
* If the value is actually null at runtime, a `
NullPointerException` will be thrown.
4. Use with Caution : * The `
!!` operator should be used sparingly and with caution because it bypasses the null safety checks provided by the Kotlin type system.
* It is typically used in situations where you have manually checked for nullability or where you are confident that a value cannot be null.
5. Preferred Approaches : * In general, it is recommended to use safe calls (`
?.`) or null checks (`
!= null`) along with safe operators like the Elvis operator (`
?:`) or safe casts (`
as?`) to handle nullable references in a safer manner.
* These approaches maintain the null safety guarantees of Kotlin and provide more robust handling of null values.
It's important to note that using the `
!!` operator excessively or without proper understanding can lead to null pointer exceptions, which Kotlin aims to prevent. Therefore, it's generally recommended to utilize safe practices and favor null safety features provided by the language whenever possible.
