Object creation, variable initialization

Question

Im reading through someone else´s code and theres this piece of code:

class Wrapper {
        UnaryOperator<String> f;
    }
    Wrapper w = new Wrapper() { // line 3
        {
            f = s -> s.length() <= 1 ? s : f.apply(s.substring(1)) + s.substring(0, 1);
        }
    };

So if i understood it correctly, he creates a new Wrapper objecet and already initializes its variable f. I´m unfamiliar with the syntax from line 4 on, i only knew something like that from anonymous classes, but this isn´t one. Can you just initializes variables in between {} after you create a new Class()? Can you also do more than that, like override or define new methods? And why do you have to put {} in between each initialization?

It **is** an anonymous class, containing an instance initializer block. This is really sloppy, though. The Wrapper class should have a better name, a constructor taking a UnaryOperator, name it correctly, and provide a getter, or even just a method delegating to the operator. Or it should simply not exist, because I don't see any value added by this class. — JB Nizet, Mar 11 '18 at 10:29

score 0 · Accepted Answer · answered Mar 11 '18 at 10:28

0

It is an Instance Initialization Block. Read more in this question

answered Mar 11 '18 at 10:28

Orest Savchak

4,529
1
18
27

Object creation, variable initialization

1 Answers1