code: public String checkProp(final Properties pr, final String name, final String defaultVal) {
      String val = pr.getProperty(name);
  
      if (val == null) {
        pr.put(name, defaultVal);
        val = defaultVal;
      }
  
      return val;
    }
docs: If the named property is present and has a value use that.
  Otherwise, set the value to the given default and use that.
  
  @param pr
  @param name
  @param defaultVal
  @return String