java - How do I add a value to a hash set? -

i'm working on practice problem requires me add value hashmap. can't figure out why keep getting error message on line coursename.add(student);

here code:

public class studentdatabase {      // add instance variables     private map<string, hashset<integer>> datacontent = new linkedhashmap<string, hashset<integer>>();      // prints report on standard output, listing courses ,     // students in each.  if map empty (no courses), prints message     // saying instead of printing nothing.     public void report() {         if (datacontent.isempty()) {             system.out.println("student database empty.");         } else {             (string key : datacontent.keyset()) {                 system.out.println(key + ":" + "\n" + datacontent.get(key));             }         }     }      // adds student course.  if student in course, no change     // if course doesn't exist, adds database.     public void add(string coursename, integer student) {         if (datacontent.containskey(coursename)) {             coursename.add(student);         } else {             set<integer> ids = new hashset<integer>();             ids.add(student);             datacontent.put(coursename, ids);         }     } } 

ok, construct:

if (datacontent.containskey(coursename)) {     coursename.add(student); } 

is whacky. want is:

if (datacontent.containskey(coursename)){     set<integer> studentsincourse = datacontent.get(coursename);     studentsincourse.add(student); } 

should fix it.