code: public boolean getBoolean(String name) {
      String valueString = getTrimmed(name);
      Preconditions.checkNotNull(valueString);
  
      valueString = valueString.toLowerCase();
  
      if ("true".equals(valueString)) {
        return true;
      } else if ("false".equals(valueString)) {
        return false;
      }
      throw new IllegalArgumentException("Configured property is not a valid boolean: name="
                                           + name + ", value=" + valueString);
    }
docs: Get the value of the <code>name</code> property as a <code>boolean</code>.
  If no such property is specified, or if the specified value is not a valid
  <code>boolean</code>, then an exception is thrown.
  
  @param name property name.
  @throws NullPointerException if the configuration property does not exist
  @throws IllegalArgumentException if the configured value is not a valid {@code boolean}
  @return property value as a <code>boolean</code>