Router and Navigation - Updating Page Title on Navigation - 《Vaadin 10 Documentation》

Setting the Page Title Dynamically

using the @PageTitle annotation
implementing HasDynamicTitle

Java

Note	The `@PageTitle` annotation is read from the actual navigation target only; neither its superclasses nor its parent views are considered.

Implementing the interface HasDynamicTitle allows us to change the title from Java at runtime:

@Route(value = "blog")
        implements HasDynamicTitle, HasUrlParameter<Long> {
  private String title = "";
  @Override
  public String getPageTitle() {
    return title;
  }
  public void setParameter(BeforeEvent event,
        @OptionalParameter Long parameter) {
      title = "Blog Post #" + parameter;
    } else {
      title = "Blog Home";
    }
  }