package com.google.sps.servlets;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;

@WebServlet("/init")
public class SessionInit extends HttpServlet {}

package com.google.sps.servlets;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseAuthException;
import com.google.firebase.auth.SessionCookieOptions;
import com.google.sps.firebase.FirebaseAppManager;
import java.io.IOException;
import java.util.concurrent.TimeUnit;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/init")
public class SessionInit extends HttpServlet {
  // Return empty string if no comment, otherwise return text
  private String getParameter(HttpServletRequest request, String name, String defaultValue) {
    String value = request.getParameter(name);
    if (value == null) {
      return defaultValue;
    } else {
      return value;
    }
  }
}

Add getParameter() to SessionInit.