java8 List集合的排序，求和，取最大值，按照条件过滤

public class Java8Test {
  
    public static void main(String[] args) {
  
        Person p1 = new Person("麻子", 31);
        Person p2 = new Person("李四", 20);
        Person p3 = new Person("王五", 26);
  
        List<Person> personList = new ArrayList<Person>();
        personList.add(p1);
        personList.add(p2);
        personList.add(p3);
  
        //java8遍历
        personList.forEach(p -> System.out.println(p.getAge()));
        //按照person的 age进行排序
        //方法一
        personList.sort((o1, o2) -> o1.getAge().compareTo(o2.getAge())); //正序
        personList.sort((o1, o2) -> o2.getAge().compareTo(o1.getAge())); //倒序
        //方法二
        personList.sort(Comparator.comparing(Person::getAge)); // 正序
        personList.sort(Comparator.comparing(Person::getAge).reversed()); // 倒序
        //遍历
        personList.forEach(p -> System.out.println(p.getAge()));
  
        System.out.println("========================================");
  
        //获取年龄最大的Person
        Person maxAgePerson = personList.stream().max(Comparator.comparing(Person::getAge)).get();
        System.out.println(maxAgePerson.getAge());
  
        System.out.println("========================================");
  
        //获取年龄最小的Person
        Person minAgePerson = personList.stream().min(Comparator.comparing(Person::getAge)).get();
        System.out.println(minAgePerson.getAge());
  
        //过滤出年龄是20的person，想过滤出什么条件的都可以
        List<Person> personList1 = personList.stream().filter(person -> person.getAge() == 20).collect(Collectors.toList());
  
        //统计出年龄等于20的个数
        long count = personList.stream().filter(person -> person.getAge() == 20).count();
  
        //获得年龄的平均值
        double asDouble = personList.stream().mapToInt(person -> person.getAge()).average().getAsDouble();
  
        //获得年龄的求和
        int sum = personList.stream().mapToInt(person -> person.getAge()).sum();
  
    }
}