3.2. Object Base Class

Java: implicit inheritance from Object (java.lang.Object):

public class Foo {
    // ...
}

Vala: no implicit inheritance from Object (GLib.Object):

public class Foo : Object {
    // ...
}

What happens if you don't inherit from Object? Nothing terrible. These classes will be slightly more lightweight, however, they will lack some features such as property change notifications, and your objects won't have a common base class. Usually inheriting from Object is what you want.