如何使用Java流从HashMaps的ArrayList中获取字符串

Question

I have a Data structure - ArrayList> and this is what I need to do -

ArrayList<HashMap<String, String>> optMapList;
//populated optMapList with some code. Not to worry abt this

List<String> values = new ArrayList<String>();

for(HashMap<String,String> entry: optMapList){
    values.add(entry.get("optValue"));
}

How do we use Java Streams to achieve the same objective?

Answer 1

 optMapList.stream()
           .filter(Objects:nonNull) // potentially filter null maps
           .map(m -> m.get("optValue"))
           .filter(Objects::nonNull) // potentially filter null values form the map 
           // .collect(Collectors.toCollection(ArrayList::new)) 
           .collect(Collectors.toList())