list 数组分类存到map中

//查询出来的所有学生List allStudents = null ;Map<String, List<Student>) map = new HashMap(

<String, List<Student>)

; for(Student student : allStudents){if(map.containsKey(student.getGroupNo())){ List students = map.get(student.getGroupNo());students.add(student);}else{ List students = new ArrayList();students.add(student); map.put(student.getGroupNo(),students);}}Student类：public class Student{private String groupNo;private String name;public String getGroupNo(){return groupNo;}public void setGroupNo(String groupNo){this.groupNo = groupNo;}public String getName(){return name;}public void setName(String name){this.name = name;}}