Java新特性解读JDK8之收集器partitioningBy和groupingBy分组函数

package com.example.streamdemo;


import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;


public class PartitioningByDemo {
  
  public static void main(String[] args) {
    List<Integer> asList = Arrays.asList(1,2,3,80,90,100);
    Map<Boolean, List<Integer>> map = asList.stream().collect(Collectors.partitioningBy(obj->obj>60));
    List<Integer> list = map.get(true);
    List<Integer> list2 = map.get(false);
    System.out.println(list);
    System.out.println(list2);
  }
}

package com.example.streamdemo;


import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;


public class GroupingByDemo {
  public static void main(String[] args) {
    //分组
    List<Person> asList = Arrays.asList(new Person(20, "jack"),new Person(20, "tony"),new Person(22, "jerry"),
        new Person(22, "marry"),new Person(25, "jony"),new Person(25, "bob"),new Person(27, "james"));
    Map<Integer, List<Person>> map = asList.stream().collect(Collectors.groupingBy(obj->obj.getAge()));
    map.forEach((key,value)->{
      System.out.println(key+"==");
      value.forEach(obj->System.out.println(obj.getName()));
      
    });
    
    //分组统计
    Map<Integer, Long> map2 = asList.stream().collect(Collectors.groupingBy(obj->obj.getAge(), Collectors.counting()));
    map2.forEach((key,value)->{
      System.out.println(key+"年龄人数:"+map2.get(key));
    });
  }


}


class Person{
  
  private int age;
  private String name;
  
  public Person() {
    super();
  }
  public Person(int age, String name) {
    super();
    this.age = age;
    this.name = name;
  }
  public int getAge() {
    return age;
  }
  public void setAge(int age) {
    this.age = age;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
}