filter

使用Stream的filter进行过滤，只保留男性的操作：

Collection<Person> collection = new ArrayList();
collection.add(new Person("张三", 22, "男"));
collection.add(new Person("李四", 19, "女"));
collection.add(new Person("王五", 34, "男"));
collection.add(new Person("赵六", 30, "男"));
collection.add(new Person("田七", 25, "女"));
Stream<Person> personStream = collection.stream().filter(new Predicate<Person>() {
    @Override
    public boolean test(Person person) {
         return "男".equals(person.getGender());//只保留男性
    }
});
collection = personStream.collect(Collectors.toList());//将Stream转化为List
System.out.println(collection.toString());//查看结果