'Casting a class to an unrelated interface

Obviously, this results in a compilation error because Chair is not related to Cat:

class Chair {}
class Cat {}

class Test {
   public static void main(String[] args) {
       Chair chair = new Char(); Cat cat = new Cat();
       chair = (Chair)cat; //compile error
   }
}

Why is it then that I only get an exception at run time when I cast a Cat reference to the unrelated interface Furniture, while the compiler can obviously tell that Cat does not implement Furniture?

interface Furniture {}

class Test {
   public static void main(String[] args) {
       Furniture f; Cat cat = new Cat();
       f = (Furniture)cat; //runtime error
   }
}
javainterfacecastingcompilationruntime


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