List<String> results = new ArrayList<String>(); --> Why do I need the braces "()" ?

Hi. Answering initial question.

ArrayList is a simple class in Java. here's the doc : https://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html

When you instantiate new instance of any class you do this:

SomeClass someClass = new SomeClass();

In this way you instantiate, i.e. create new instance of the class SomeClass using default constructor.

That is exactly what we do with ArrayList<>(), we instantiate ArrayList class with default constructor.

Does it makes sense?

Coming back to arrays: Arrays are primitives, they are not classes, so you cannot write like this:

There are different ways to instatiate array. Take a look here, e.g.

http://alvinalexander.com/blog/post/java/java-faq-create-array-int-example-syntax

The most important when you instantiate array - is to set its size: You have to know size when you instantiate array. That's why the easiest way to create array is to write:

String[] test = new String[3];

This way you are creating array with length of 3, and type String.