java - 如何用字符串过滤我的列表？

Question

有人可以解释一下为什么我无法通过 .stream().filter 过滤列表中的字符串吗？我收到的只是未经过滤的字符串! 我会很感激的。

public static void main(String[] args) throws FileNotFoundException {

        List<Country> countries = CsvToBeanConverterCountry("country.csv");
        countries
                .stream().filter(s -> s.getName().contains("xx")).collect(Collectors.toList());
        countries.forEach(s -> System.out.println(s.getName()));
    }

    private static List CsvToBeanConverterCountry(String csvFilename) throws FileNotFoundException {

        CsvToBean csv = new CsvToBean();
        CSVReader csvReader = new CSVReader(new FileReader(csvFilename), ';', '"', 1);
        List list = csv.parse(setColumMappingCountry(), csvReader);
        return list;
    }

    private static ColumnPositionMappingStrategy setColumMappingCountry() {
        ColumnPositionMappingStrategy strategy = new ColumnPositionMappingStrategy();
        strategy.setType(Country.class);
        String[] columns = new String[]{"country_id", "city_id", "name"};
        strategy.setColumnMapping(columns);
        return strategy;
    }
}

Answer 1

您忽略了收集的结果:

countries.stream().filter(s -> s.getName().contains("xx"))
         .collect(Collectors.toList());

因此您应该将结果分配给一个新列表并仅打印该列表

List<Country> result = countries.stream()...
result.forEach(...)