筛选，是按照一定的规则校验流中的元素，将符合条件的元素提取到新的流中的操作。

「案例一：筛选出Integer集合中大于7的元素，并打印出来」

public class StreamTest {public static void main(String[] args) {List<Integer> list = Arrays.asList(6, 7, 3, 8, 1, 2, 9);Stream<Integer> stream = list.stream();stream.filter(x -> x > 7).forEach(System.out::println);}
}

「案例二：筛选员工中工资高于8000的人，并形成新的集合。」 形成新集合依赖collect（收集），后文有详细介绍。

public class StreamTest {public static void main(String[] args) {List<Person> personList = new ArrayList<Person>();personList.add(new Person("Tom", 8900, 23, "male", "New York"));personList.add(new Person("Jack", 7000, 25, "male", "Washington"));personList.add(new Person("Lily", 7800, 21, "female", "Washington"));personList.add(new Person("Anni", 8200, 24, "female", "New York"));personList.add(new Person("Owen", 9500, 25, "male", "New York"));personList.add(new Person("Alisa", 7900, 26, "female", "New York"));List<String> fiterList = personList.stream().filter(x -> x.getSalary() > 8000).map(Person::getName).collect(Collectors.toList());System.out.print("高于8000的员工姓名：" + fiterList);}
}