java8 stream 流式编程

list转map

@Data
public class Person {
    private String id;
    private String name;
    private int age;

    public Person(String id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
}

public class StreamTest {

    public static void main(String[] args) {
        List<Person> people = new ArrayList<>();
        Person person1 = new Person("1", "张三", 10);
        Person person2 = new Person("2", "李四", 20);
        Person person3 = new Person("3", "王五", 10);
        people.add(person1);
        people.add(person2);
        people.add(person3);

        // list 转 map
        Map<String, Person> collect = people.stream().collect(Collectors.toMap(Person::getId, k -> k));
        // System.out::println 可以看作 lambda表达式 e -> System.out.println(e) 的缩写形式。
        collect.values().forEach(System.out::println);
    }
}

过滤

public class StreamTest {

    public static void main(String[] args) {
        List<Person> people = new ArrayList<>();
        Person person1 = new Person("1", "张三", 10);
        Person person2 = new Person("2", "李四", 20);
        Person person3 = new Person("3", "王五", 10);
        people.add(person1);
        people.add(person2);
        people.add(person3);

        // list 过滤年龄==10的 
        List<Person> collect = people.stream().filter(p -> p.getAge() == 10).collect(Collectors.toList());
        collect.forEach(System.out::println);
    }
}

分组操作

Map<String, List<DoExtchCfg>> channelMap =  doExtchCfgs.stream().collect(Collectors.groupingBy(DoExtchCfg::getExtChannelCode));