Gamer.java

// Gamer.java
import [...]

public final class Gamer {
   @NotNull
   private final String username;

   @NotNull
   public final String getUsername() {
      return this.username;
   }

   public Gamer(@NotNull String username) {
      Intrinsics.checkParameterIsNotNull(username, "username");
      super();
      this.username = username;
   }
}