Why can a class instance be converted to an interface without implementation relationship, but not to a class without inheritance relationship?

Question

I have a Person class and an empty class called MyClass and an empty interface called MyInterface. There is no relationship between the Person, MyClass and MyInterface.

When I cast a Person instance to MyInterface, the compilation passes, but when I cast a Person instance to MyClass, the compilation fails. Why is that?

Below is my code:

class Person {
    public String name;
}

class MyClass {}

interface MyInterface {}

class Test {
    public static void main(String[] args) {
        // Compile passed
        MyInterface myInterface = (MyInterface) new Person();

        // Compile error
        MyClass myClass = (MyClass) new Person();
    }
}