stream根据某个字段进行分组统计

方法一：

//先分组
Map<String, List<Student>> map = list.stream().collect(
		Collectors.groupingBy(Student::getName));
//再排序
for (Map.Entry<String, List<Student>> nmap : map.entrySet()) {
   nmap.getValue().sort(Comparator.comparing(Student::getScore));
}

方法二：

//分组排序
Map<String, List<Student>> map = list.stream().collect(
	Collectors.groupingBy(Student::getName, HashMap::new, 		
      Collectors.collectingAndThen(Collectors.toList(),
      //正序
	  list -> list.stream().sorted(Comparator.comparing(Student::getScore)) 
  //倒序
  //list -> list.stream().sorted(Comparator.comparing(Student::getScore).reversed()) 
	    .collect(Collectors.toList())
)));

原文链接