IronIcon in Java

I don’t see the icon.What am i missing here ? Please suggest.

import com.vaadin.flow.component.icon.IronIcon;

IronIcon ironIcon = new IronIcon("icons","save");
Button buttonIron = new Button("test",ironIcon);
add(buttonIron);

When using Flow, I recommend to use just Icon component of Flow, as you see from documentation here, it is implemented by using iron-icon and our VaadinIcons set of icons.

https://vaadin.com/api/platform/11.0.2/com/vaadin/flow/component/icon/Icon.html

IronIcon is for the case that you have some other set of icons, but then you need to also provide the icon set for it.