Using constants efficiently

In Java, constants are typically static members of a class. Kotlin introduces companion objects for a similar purpose, but there are more efficient ways of handling constants in Kotlin.

Initially, one might define constants in Kotlin using a companion object:

class Spock {
    companion object {
        val SENSE_OF_HUMOR = "None"
    }
}

However, this approach has some inefficiencies. The Kotlin compiler generates a getter for the constant, introducing an additional layer of indirection. The code using the constant effectively calls a getter method, which is less efficient.

Using JVM pseudocode, the results may look as follows:

String var0 = Spock.Companion.getSENSE_OF_HUMOR();
System.out.println(var0);

To optimize, you can use the const keyword:

class Spock {
    companion object {
        const val SENSE_OF_HUMOR = "None"
    }
}

This modification leads to more efficient bytecode:

public class...