java中stream处理

JAVA8中引入了lamda表达式和Stream接口。其丰富的API及强大的表达能力极大的简化代码，提升了效率。

下面记录下stream处理功能

Person只是简单的实体类

@Data
public class Person {


   private Integer    id;
   private   String name;
    private  String sex;
    private  Long  height;
}

 

  List<Person> peopleList=Person.constructPersons();

         Person person=new Person();
         person.setName("name0");
         peopleList.add(person);

         logger.info("原始数据:{}",JSON.toJSON(peopleList));

         List<String> list = peopleList.stream().map(Person::getName).collect(Collectors.toList());

         logger.info("返回List数据:{}",JSON.toJSON(list));

         Set<String> set = peopleList.stream().map(Person::getName).collect(Collectors.toCollection(TreeSet::new));

         logger.info("返回Set数据:{}",JSON.toJSON(set));
         String joined = peopleList.stream()
                 .map(Person::getName)
                 .collect(Collectors.joining("|"));
         logger.info("返回String数据:{}",JSON.toJSON(joined));


         Long total = peopleList.stream()
                 .collect( Collectors.summingLong(Person::getMillis));
         logger.info("返回Long数据:{}",JSON.toJSON(total));

         Map<String, List<Person>> byDept
                 = peopleList.stream()
                 .collect(Collectors.groupingBy(Person::getName));
         logger.info("返回Map数据:{}",JSON.toJSON(byDept));

         Map<String,Long> totalByDept
                 = peopleList.stream()
                 .collect(Collectors.groupingBy(Person::getName,Collectors.summingLong(Person::getMillis)));
         logger.info("返回totalByDept数据:{}",JSON.toJSON(totalByDept));

         Map<Boolean, List<Person>> passingFailing =
                 peopleList.stream()
                         .collect(Collectors.partitioningBy(s -> s.getId() >= 3));

         logger.info("返回passingFailing数据:{}",JSON.toJSON(passingFailing));