Experiment trying to create a builder pattern which enforces certain params and others being optional, that's also inheritable.

ComposableBuilder.java

public class Activity1$$IntentBuilder<NEXT> {

    protected Map<String, String> params = new HashMap<>();

    public Activity1FirstParam createActivity1() {
        return new Activity1FirstParam();
    }

    protected class Activity1FirstParam {
        public AfterExtra1 extra1(String extra1) {
            params.put("extra1", extra1);
            return new AfterExtra1();
        }
    }

    public class AfterExtra1 {
        public NEXT extra2(String extra2) {
            params.put("extra2", extra2);
            return createAllSet();
        }
    }

    public NEXT createAllSet() {
        return (NEXT) new Activity1AllSet();
    }

    public class Activity1AllSet {
        public Activity1AllSet optional1(String optional1) {
            params.put("optional1", optional1);
            return this;
        }

        public Map<String, String> build() {
            return params;
        }
    }
}

public class Activity2$$IntentBuilder<NEXT> extends Activity1$$IntentBuilder<NEXT> {

    public Activity2FirstParam createActivity2() {
        return new Activity2FirstParam();
    }

    public class Activity2FirstParam {
        public AfterExtra3 extra3(String extra3) {
            params.put("extra3", extra3);
            return new AfterExtra3();
        }
    }

    public class AfterExtra3 {
        public Activity1FirstParam extra4(String extra4) {
            params.put("extra4", extra4);
            return new Activity1FirstParam();
        }
    }

    @Override
    public NEXT createAllSet() {
        return (NEXT) new Activity2AllSet();
    }

    public class Activity2AllSet extends Activity1AllSet {
        public Activity2AllSet optional2(String optional2) {
            params.put("optional2", optional2);
            return this;
        }
        public Activity2AllSet optional3(String optional3) {
            params.put("optional3", optional3);
            return this;
        }
    }
}

public class Client {
    public static void main(String[] args) {
        Map<String, String> params1 = new Activity1$$IntentBuilder<Activity1$$IntentBuilder.Activity1AllSet>().createActivity1()
                .extra1("first")
                .extra2("second")
                .optional1("hello")
                .build();

        printMap(params1);

        Map<String, String> params2 = new Activity2$$IntentBuilder<Activity2$$IntentBuilder.Activity2AllSet>().createActivity2()
                .extra3("3")
                .extra4("4")
                .extra1("1")
                .extra2("2")
                .optional3("op3")
                .build();

        System.out.println("#########################");
        printMap(params2);
    }

    private static void printMap(Map<String, String> params1) {
        for (String key : params1.keySet()) {
            System.out.println(key + " : " + params1.get(key));
        }
    }
}