On JVM 14, you can activate 'helpful' NPEs with the -XX:+ShowCodeDetailsInExceptionMessages flag. In the latest versions of the JVM, the language designers improved the situation. Running this snippet may result in something like the following: Exception in thread 'main' Īt ch.(NpeSample.java:10)Īt this point, you have no clue which part is null in the call chain: foo, or the value returned by getBar() or getBaz()?

var value = foo.getBar().getBaz().toLowerCase() The reason for the NPE is calling a method or accessing an attribute of an object that has not been initialized. Java has long been infamous for its NullPointerException. Now let’s see how our test would look like.Nicolas is a developer advocate with 15+ years experience consulting for many different customers, in a wide range of contexts (such as telecoms, banking, insurances, large retail and public sector). Our domain objects would be the following classes then.ĭata class Customer(val name: String, val address: Address?) Therefore we’d like to update in our database just those customers with an existing address. We also know that the address has been optional for many years, so not all of our customers have an address. The requirement is to update the address to a new format where each field is contained in a different field. For instance, we could have an address like this '22 Baker Street - W1U8ED England'. `should add 1 to each element in the list`() “. This method applies a function to each element contained in a collection, creating a new collection with the new elements as a result. The most common way of transforming elements in a collection is by using map method.

Photo by SOULSANA on Unsplash Regular Kotlin map method

Kotlin map not null