public final void initId(ComponentId id) {
        if (this.id != null && !this.id.equals(id))
            throw new RuntimeException("Can't change component id: " + this.id + " -> " + id);

        if (id==null) throw new NullPointerException("A component cannot be created with a null id");
        this.id=id;
    }
Initializes this. Always called from a constructor or the framework. Do not call.
component/src/main/java/com/yahoo/component/AbstractComponent.java