code: public static String getEnv(String name, String defaultValue) {
          Map<String, String> env = System.getenv();
  
          // try to get value from environment variables
          if (env.get(name) != null) {
              return env.get(name);
          }
  
          // fall back to system properties
          return System.getProperty(name, defaultValue);
      }
docs: returns values for a key in the following order:
  1. First checks environment variables
  2. Falls back to system properties
  
  @param name
  @param defaultValue
  @return