code: public static String getString(Properties props, String name, String defaultValue) {
          return props.containsKey(name) ? props.getProperty(name) : defaultValue;
      }
docs: Get a string property, or, if no such property is defined, return
  the given default value
  
  @param props        the properties
  @param name         the key in the properties
  @param defaultValue the default value if the key not exists
  @return value in the props or defaultValue while name not exist