Java Casting Interface to Class

Question

public class InterfaceCasting {

    private static class A{}

    public static void main(String[] args) {
        A a = new A();
        Serializable serializable          


        

Answer 1

Serializable serializable;
a = (A)serializable;

As for the compiler, the variable serializable can contain any object that implements Serializable, which includes subclasses of A. So it assumes that you know that the variables indeed contains an A object and allows that line.