LinkedList<String> modelValue = new LinkedList<>();
componentValue.forEach(product -> {
    Product p = (Product) product;
    modelValue.add(p.getObjectId());
});

Method 'Iterable.forEach(Consumer<? super T>)' is not present in JRE Emulation Library so it cannot be used in client code of 'com.mycompany.app.AppTest' GWT module less... (Ctrl+F1)
This inspection reports usages in client code of JDK classes which are not present in the JRE Emulation Library.