jdk8新特性Stream

        Person p1 = new Person();
        p1.setName("P1");
        p1.setAge(10);
        Person p2 = new Person();
        p2.setName("pp2");
        p2.setAge(9);
        Person p3 = new Person();
        p3.setName("p3");
        p3.setAge(5);
        List<Person> list = new ArrayList<>();
        list.add(p1);
        list.add(p2);
//若最后不添加collect方法，则返回类型是stream
        list = list.stream().filter(person ->   person.getAge()>5).collect(Collectors.toList());
        System.out.println(list);

输出结果：
[Person{name=‘P1‘, age=10}, Person{name=‘pp2‘, age=9}]

List<String> list = Stream.of("a","b","wo").map(string -> string.toUpperCase()).collect(Collectors.toList());
System.out.print(list);

输出结果：
[A, B, WO]

List<Integer> list = Stream.of("1","2").mapToInt(e ->Integer.parseInt(e)).boxed().collect(Collectors.toList());
//maptoInt之后是IntStream类型，需要用boxed转换为Stream