Optional

判断 对象是否为空

Optional.ofNullable(queueWhiteOne).isPresent())

//防止对象空指针异常

Optional.ofNullable(list).orElse(Lists.newArrayList());
public static void main(String[] args) {
        List<String> list = null;
        List<String> newList = Optional.ofNullable(list).orElse(Lists.newArrayList());
        newList.forEach(x -> System.out.println(x));