Differences in style between Java and Scala code

If you are going to refactor or rewrite Java code into Scala code, there are a number of style differences that are useful to be aware of. Obviously, programming style is largely a matter of taste; however, a few guidelines generally acknowledged by the Scala community can help someone new to Scala to write easier-to-read and more maintainable code. This section is dedicated to showing some of the most common differences.

Writing an algorithm in Java follows an imperative style, that is, a sequence of statements that change a program state. Scala, focusing primarily on functional programming, adopts a more declarative approach, where everything is an expression rather than a statement. Let's illustrate this in an example.

In Java, you would commonly find the following code snippet:

...
String customerLevel = null;
if(amountBought > 3000) {
    customerLevel = "Gold"; 
} else {
    customerLevel = "Silver";
}
...

The Scala equivalent consists...