Kotlin Programming: The Big Nerd Ranch Guide, First Edition

For the More Curious: A Closer Look at var and val Properties

In this chapter you learned that the var and val keywords are used when specifying a class property – var for writable, and val for read-only.

You may be wondering how a Kotlin class property works, under the hood, when targeting the JVM.

To understand how class properties are implemented, it is helpful to look at the decompiled JVM bytecode – specifically, to compare the bytecode generated for a single property depending on how it is specified. Create a new file called Student.kt. (You will delete this file after this exercise.)

First, define a class with a var property (which allows both reading and writing the class property).

Listing 12.23  Defining a Student ...