In a previous post I explained what Kotlin Object Declarations are. This time around it’s about the declaration’s sibling, the Object Expression.

An object is not just a glorified static replacement or a singleton. object can be used where Java usually utilizes anonymous inner classes. Let’s look at a more realistic scenario: a JButton and an ActionListener or a MouseListener.

Instead of implementing my own backup application as I had planned a long time ago, I’m wandering off (re)learning Kotlin after a long absence from that language. In my defense though, I’m doing it in the context of the backup app which will not be Java as originally intended (or maybe later for comparison, who knows, I obviously can’t be trusted with my plans). Putting that aside, the most confusing concept of Kotlin for a Java developer is the object. What is that thing doing that a class can’t do and how do we declare static fields and methods? I know it’s nothing new, but that part seems to have changed a bit since I used Kotlin about two (?) years ago. So, for me this is a refresh of old information and also something new and by writing about it I will engrave it in my brain once and for all. And your confusion will hopefully turn into some productive… fusion… of some sort… or so.