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();

 

    }

}