How we detect

public final class BadInstanceOf {

public static void doSomething(Animal aAnimal){
if (aAnimal instanceof Fish){
Fish fish = (Fish)aAnimal;
fish.swim();
}
else if (aAnimal instanceof Spider){
Spider spider = (Spider)aAnimal;
spider.crawl();
}
}

// PRIVATE //
private static class Animal {}

private static final class Fish extends Animal {
void swim(){}
}
private static final class Spider extends Animal {
void crawl(){}
}
}

Remedy –

public final class BadInstanceOfFixed {

public static void doSomething(Animal aAnimal){
//calls different versions of move, specific to
//each Animal
aAnimal.move();
}

// PRIVATE //
private static class Animal {
void move(){
//do nothing
}
}

private static final class Fish extends Animal {
void move(){
//move like a fish
}
}
private static final class Spider extends Animal {
void move(){
//move like a spider
}
}
}

This report lists all artifacts that reference instanceOf used with an internal class or interface as argument.
It provides the following information:
Artifact full name, the number of occurrences of this detected in the artifact