public abstract class Class1 extends Class2{
    public Class1(){
        Class4.doSomething(new Class3(this));
    }
}

public abstract class Class2{
    // Stuff
}

public class Class3{
    public Class3(Class2 instance){
        // Stuff
    }
}

public class Class4{
    public static void doSomething(Class3 instance){
        // Stuff
    }
}