Java interface throws an exception but interface implementation does not throw an exception?

Question

I read this code where the interface throws an exception, but the class which implements it doesn\'t throw one or catch one, why is that? Is it legal or safe in java?

Answer 1

If a Java method overrides another in a parent class, or implements a method defined in an interface, it may not throw additional checked exceptions, but it may throw fewer.

public class A {
    public void thrower() throws SQLException {...}
}

public class B extends A {
    @Override
    public void thrower() throws SQLException, RuntimeException, NamingException {...}
}

SQLException is fine; it's declared in the overridden method. It could even be replaced by a subclass like SerialException.

RuntimeException is fine; those can be used anywhere.

NamingException is illegal. It isn't a RuntimeException, and isn't in A's list, even as a subtype.