Java Streams - check if list is null-CodePudding

I wonder what's teh best approach to check if list is null. In my Stream I call orElseThrow twice. It works but I don;t know if its correct? It looks a little bit ugly:

Optional.ofNullable(listCanBeNull)
                .orElseThrow(() -> new ResourceNotFoundException("the same error message"))
                .stream()
                .filter(configuration -> configuration.getId().equals(warehouseConfigurationId))
                .findAny()
                .orElseThrow(() -> new ResourceNotFoundException("the same error message"));

I have to throw error when list is null and when no item was found

CodePudding user response：

Just check if the list is null directly. Streaming elements from a list only makes sense if the list exists in the first place.

if(null != listCanBeNull) {
    // stream things from here
}

CodePudding user response：

An Optional.ofNullable can be turned into a (possibly empty) Stream, or you can immediately use Stream.ofNullable. And do a flatMap.

Stream.ofNullable(listCanBeNull)
        .stream()
        .flatMap()
        .filter(configuration -> couration.getId().equals(warehouseConfigurationId))
        .findAny()
        .orElseThrow(() -> new ResourceNotFoundException("the same error message"));