Java8 Stream Lambda

1、Stream的聚合操作
例子：对集合对象进行排序、取值操作（使用2种实现方式）
User liLei = new User(1, "liLei", 28, (short)0);User hanMeiMei = new User(2, "hanMeiMei", 25, (short)1);User zhou = new User(3, "zhou", 30, (short)1);User wu = new User(4, "wu", 32, (short)1);User zheng = new User(5, "zheng", 29, (short)0);List<User> users = new ArrayList<>();users.add(liLei);users.add(hanMeiMei);users.add(zhou);users.add(wu);// 按年龄从小到大输出年龄大于20的男性用户姓名// 实现方式一：List<User> userList = new ArrayList<>();for (User user: users) {    if (user.getAge() > 20 && user.getSex() == 1) {        userList.add(user);    }}Collections.sort(userList, new Comparator<User>() {    @Override    public int compare(User o1, User o2) {        return o1.getAge().compareTo(o2.getAge());    }});List<String> names = new ArrayList<>();for (User user: userList) {    names.add(user.getName());}System.out.PRintln(names);// 实现方式二：List<String> nameList = users.stream()        .filter(user -> user.getAge() > 20 && user.getSex() == 1)        .sorted(Comparator.comparing(User::getAge).reversed())        .map(User::getName)        .collect(Collectors.toList());System.out.println(names);
 
结果输出：
[hanMeiMei, zhou, wu]
[hanMeiMei, zhou, wu]
第二种实现方式相比第一种实现方式，更方便高效。
java8的Stream借助Lambda表达式提高了编程速度和程序易读性。