Demonstrates how much boilerplate is removed by using Kotlin's `firstOrNull{}` extension.

Test.java

public static String getKeyForClass(Class<?> classToCheck) {
    int index = -1;
    int internalClassesLength = ManagerRegistry.INTERNAL_CLASSES.size();

    // Check if this class has a superclass defined in this project.
    for (int i = 0; i < internalClassesLength; i++) {
        if (ManagerRegistry.INTERNAL_CLASSES.get(i).isAssignableFrom(classToCheck)) {
            index = i;
            break;
        }
    }

    Class keyClass = index > -1
            // Use the class of the internal version
            ? ManagerRegistry.INTERNAL_CLASSES.get(index)
            // Otherwise use the original class
            : classToCheck;

    return keyClass.getCanonicalName();
}

Test.kt

fun getKeyForClass(classToCheck: Class<*>): String {
    val keyClass = RManagerRegistry.INTERNAL_CLASSES.firstOrNull { it.isAssignableFrom(classToCheck) } ?: classToCheck
    return keyClass.canonicalName
}