jdk1.8特性lambda和stream操作集合你都用过?

     public static void main(String[] args) {
        List<Developer> listDevs = getDevelopers();
        //lambda 按名称排序
        listDevs.sort((Developer o1, Developer o2) -> o1.getName().compareTo(o2.getName()));
        System.out.println("按名称排序：" + JSON.toJSONString(listDevs));
        //lambda 按名称排序
        listDevs.sort((o1, o2) -> o1.getName().compareTo(o2.getName()));
        System.out.println("按名称排序：" + JSON.toJSONString(listDevs));
        //lambda 按名称排序
        listDevs.sort(Comparator.comparing(Developer::getName).reversed());
        System.out.println("按名称排序：" + JSON.toJSONString(listDevs));
        List<Developer> developersGroup = getDevelopersGroup();
        //stream 按名称分组
        Map<String, List<Developer>> developersGroupMap = developersGroup.stream().collect(Collectors.groupingBy(Developer::getName));
        System.out.println("按名称分组：" + JSON.toJSONString(developersGroupMap));
        List<Integer> ageList = new ArrayList<>();
        ageList.add(20);
        ageList.add(20);
        ageList.add(10);
        ageList.add(10);
        ageList.add(11);
        //stream 对list分组统计
        Map<Integer, Long> collect = ageList.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
        System.out.println("对list分组统计：" + JSON.toJSONString(collect));
    }
    private static List<Developer> getDevelopers() {
        List<Developer> result = new ArrayList<Developer>();
        result.add(new Developer("mkyong", new BigDecimal("70000"), 33));
        result.add(new Developer("alvin", new BigDecimal("80000"), 20));
        result.add(new Developer("jason", new BigDecimal("100000"), 10));
        result.add(new Developer("iris", new BigDecimal("170000"), 55));
        return result;

    }
    private static List<Developer> getDevelopersGroup() {
        List<Developer> result = new ArrayList<Developer>();
        result.add(new Developer("mkyong", new BigDecimal("70000"), 33));
        result.add(new Developer("mkyong", new BigDecimal("80000"), 20));
        result.add(new Developer("jason", new BigDecimal("100000"), 10));
        result.add(new Developer("jason", new BigDecimal("170000"), 55));
        return result;
    }

输出结果

按名称排序：[{"age":20,"bigDecimal":80000,"name":"alvin"},{"age":55,"bigDecimal":170000,"name":"iris"},{"age":10,"bigDecimal":100000,"name":"jason"},{"age":33,"bigDecimal":70000,"name":"mkyong"}]
按名称排序：[{"age":20,"bigDecimal":80000,"name":"alvin"},{"age":55,"bigDecimal":170000,"name":"iris"},{"age":10,"bigDecimal":100000,"name":"jason"},{"age":33,"bigDecimal":70000,"name":"mkyong"}]
按名称排序：[{"age":33,"bigDecimal":70000,"name":"mkyong"},{"age":10,"bigDecimal":100000,"name":"jason"},{"age":55,"bigDecimal":170000,"name":"iris"},{"age":20,"bigDecimal":80000,"name":"alvin"}]
按名称分组：{"mkyong":[{"age":33,"bigDecimal":70000,"name":"mkyong"},{"age":20,"bigDecimal":80000,"name":"mkyong"}],"jason":[{"age":10,"bigDecimal":100000,"name":"jason"},{"age":55,"bigDecimal":170000,"name":"jason"}]}
对list分组统计：{20:2,10:2,11:1}