java - Generics and ArrayList -

how can access methods in students class. when print mylist uses tostring in students class, i'm not sure how access other methods. possible?

ps have try , catch in program, didn't post here make code shorter.

public class databaseaccess <t> {     public t[] database;     public arraylist<t>mylist = new arraylist<t>();     public arraylist<t> testlist = new arraylist<t>();     public void userinterface(){     int count = 1;         (t : mylist){              system.out.println(count++ + ": " + i);              }     }     public void readdatabase(){         try {                 objectinputstream in = new objectinputstream(new fileinputstream("grocery.bin"));                 database = (t[]) in.readobject();                     (int = 0; < database.length; i++){                         mylist.add(database[i]);                     }                 mylist.add((t) "\n");                 mylist.add((t)  "\tstudents:");                 objectinputstream in1 = new objectinputstream(new fileinputstream("students.bin"));                 database = (t[]) in1.readobject();                     (int = 0; < database.length; i++){                          mylist.add(database[i]);                     }     } }         public class student implements serializable, comparable{      private string name, id, address;      private double gpa;       public student(string name, string id, double gpa){          this.name = name;          this.id = id;          this.gpa = gpa;      }      public int compareto(object object){          student student = (student ) object;          if(this.gpa < student.getgpa())               return -1;          else                if(this.gpa > student.getgpa())             return 1;                else                     return 0;      }      public string getname(){ return name;}      public string getid(){ return id;}      public double getgpa(){ return gpa;}      public string tostring(){ return (string.format("%16s%10.4s%8s", name, id, gpa));} } 

assuming mean within databaseaccess, in theory, don't.

now, use following, horrible idea , absolutely reeks of bad design (no offense meant - don't want give impression code @ okay or should use - technically possible):

 (t t : mylist) {     if (t instanceof student) {       student student = (student) t;       student.getgpa();     } else if (t instanceof food) {       ...     }  } 

as far databaseaccess concerned, it's not student. it's random object of type t know nothing about. if can't create common interface between student , food want, have ask why databaseaccess needs know specifics of classes , figure out design should separate things more sanely.

are doing custom printing? maybe formatting should done within student/food class.

are you, e.g. processing user input , manipulating data objects in database? separate concerns of database access , data manipulation. changing gpa shouldn't require know whether data being stored in objectoutputstream or oracle database. so, have databaseaccess deal database, , define other class works databaseaccess<student> through defined interface, , have handle student-specific manipulation.

without knowing precisely you're trying do, it's hard give solid advice beyond: if think need you're asking, might want step , think if there might better way approach problem don't.