When developing Android applications in Java, NullPointerException (NPE) was a big problem. At execution time, the reference to object can be void, leading to run-time exceptions (In the case of Java, a NullPointerException) and often abnormal termination of the program. A typical function call is of the form object.func() object denotes a reference to a certain object, and func denotes a function call. In object-oriented languages, access to objects is achieved through references. Null Safety (or void safety) is the guarantee that no object reference will have a null value. This document explains Kotlin's null safety feature. But I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement.” It was the invention of the null reference…My goal was to ensure that all use of references should be absolutely safe, with checking performed automatically by the compiler. This can make the code more self-documenting and easier to read.“I call it my billion-dollar mistake. ![]() The developer can be aware of this and use alternatives like top-level functions or extension functions. Kotlin string literals can become difficult to read if multiple if cases are used to construct them. This solution could seem like the most human-readable way of conveying the purpose of our code: appending a sentence only if its contents are not null. One of the solutions would be to check the null value with elvis(?:) operator: var result = "First is $ What if the goal is to concatenate only if the second string is not null? There are a few options: if-else Println("First is $first and second is $second") A null String is concatenated as “null” in Kotlin: val first:String? = "first"
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