stream-1.java

List<String> strList = Stream.of("1", "2", "illegal_3", "4", "illegal_5", "6").collect(Collectors.toList());
 
//return null and filter null
intList = strList.stream()// same with "parallelStream()"
            .map(x -> {
                try {
                    return Integer.parseInt(x);
                } catch (NumberFormatException nfe) {
                    System.err.println(nfe.getMessage());
                }
                return null;
            })
            .filter(x -> x!= null)
            .collect(Collectors.toList());
 

 
intList = strList.stream()
            .flatMap(x -> parseIntStream(x))
            .collect(Collectors.toList());
 
//return empty stream if error
static Stream<Integer> parseIntStream(String s) {
    try {
        return Stream.of(Integer.parseInt(s));
    } catch (NumberFormatException nfe) {
        System.err.println(nfe.getMessage());
    }
    return Stream.empty();
}