Sealed class hieararchy "implementation"

DefaultSealedServices.java

public final class DefaultSealedServices extends SealedServices {
    private FooService fooService;
    private BarService barService;

    // We don’t want the client to instantiate this class
    DefaultSealedServices(FooService fooService, BarService barService) {
        this.fooService = fooService;
        this.barService = barService;
    }

    @Override
    public FooService getFooService() {
        return fooService;
    }

    @Override
    public BarService getBarService() {
        return barService;
    }

    @Override
    void validate() {
        Validate.notNull(this.fooService);
        Validate.notNull(this.barService);
    }

}