August 2021
Intermediate to advanced
422 pages
10h 18m
English
Content preview from Java to Kotlin
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Chapter 5. Beans to Values
Many Java projects have settled on mutable JavaBeans or POJO (plain old Java object) conventions for representing data. Mutability brings complications, though. Why are immutable values a better choice, and how can we reduce the cost of mutability in a codebase?
Beans
As we discussed in “Bean Style”, JavaBeans were introduced to allow the development of drag-and-drop GUI builders in the Visual Basic style. A developer could drop a button onto a form, change its title and icon, and then wire in an on-click handler. Behind the scenes, the GUI builder would write code to instantiate a button object and then call setters for the properties that the developer had changed.
To define a JavaBean, a class needs a default (no-argument) constructor, getters for its properties, and setters for its mutable properties. (We’ll gloss over the Serializable requirement, because even Sun never really took this seriously.)
This makes sense for objects that have a lot of properties.
GUI components typically have foreground and background colors, font, label, borders, size, alignments, paddings, and so on.
Mostly the defaults for these properties are fine, so calling setters for just the special values minimizes the amount of code to be generated.
Even today, a mutable component model is a solid choice for GUI toolkits.
When JavaBeans were introduced, though, we thought of most objects as mutable, not just UI components. I mean, why not? The point of objects was to encapsulate ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.