private void verifyBooleanString(String propertyString, String property) {
    if (!(propertyString.equalsIgnoreCase("true") || propertyString.equalsIgnoreCase("false"))) {
      throw new IllegalArgumentException(
          String.format("%s property has to be true or false or null and cannot be %s",
              property, propertyString));
    }
  }
Verifys if the propertyString passed is a valid boolean value or null else throws an
IllegalArgument exception

@throws IllegalArgumentException if the property string passed does not represent a boolean or
        null
geode-core/src/main/java/org/apache/geode/internal/cache/DiskWriteAttributesImpl.java