We went from two Java classes to two Kotlin ones that now look like this: Here's a TL;DR of the Java functionalities and their mapping to Kotlin: fields and functions declared in a companion object. Find out more about initializer blocks from the official documentation. Our UI logic displays "Unknown" in case the first and last names are missing, so we're not supporting null objects. If your function has multiple parameters, consider using named arguments as they make the code more readable. I was recently involved in quite a long Twitter discussion regarding Java's Optional, type systems that distinguish nullable and non-nullable types and the Elvis operator, which allows null-safe member selection.The latter was peddled as a killer feature for succinct null-handling, which I strongly disagree with. This project provides the implementation of an Elvis operator and the code samples from a CodeFX blog about it. Work fast with our official CLI. Then we'll take a look at the converted code and see how we can improve it by making it more idiomatic and avoid common pitfalls. : 'default'}") // Will inject provided string if someProperty is null private String elvis; 2.5. As a result, for all the usages of the users object, the not-null assertion operator !! :); if you view it sideways, it reminds you of Elvis Presley. operator converts any variable to a non-null type, so you can access properties or call functions on it. using val instead of var) and avoiding nullable types. With the absence of an Elvis (existential) operator in JavaScript, I often find myself writing the same checks to see if something is undefined over and over and over again. This block's only purpose is to initialize the name value. エルビス演算子 (英語: elvis operator) は、いくつかのプログラミング言語にある演算子で、字句構文は ? Highlight the variable name, right click to Refactor > Rename the variable. :, or or ||, is a binary operator that returns its first operand if that operand evaluates to a true value, and otherwise evaluates and returns its second operand. If you're using IntelliJ IDEA, create a new Java project with Kotlin/JVM. val is similar to the final keyword in Java. This can be contrasted with the logical OR (||) operator, which returns the right-hand side operand if the left operand is any falsy value, not only null or undefined.

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