Can somebody help me understand the following code?

Question

public static ArrayList<Words> extractData(String requestUrl) {
URL url = createUrl(requestUrl); //1
jsonResponse = makeHttpRequest(url); //2
ArrayList<Words> jsonData = extractJSON(jsonResponse); //3
return jsonData; //4
}
public static ArrayList<Words> extractJSON(String JSON_String){
ArrayList<Words> words = new ArrayList<Words>();
//some code
return words;
}

i understand //1 converting string to URL
//2 making http request and storing the data in jsonResponse
What does //3 //4 mean?

Answer 1

it converts (parse) data from String jsonResponse to ArrayList<Words>
and return data in ArrayList instead in String

ArrayList<Words>
is like array of Objects, you can imagine it like as
Object[] jsonData = new Object[size];
here are stored objects of type Words, Words is some class, so it is like
Words[] jsonData = new Words[size];

More precisely ArrayList is resizable ordered collection (group of objects) from Collections framework.
It is a 'generic class' and stores objects of generic type that is unknown in advance and is determined by a 'diamond' syntax <Type> when this array is declared by programmer. Here it is type <Words>.

https://www.sololearn.com/learn/Java/2179/?ref=app
https://docs.oracle.com/javase/tutorial/java/generics/types.html
https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html