java - IndexOutOfBoundException on method called in a JSP Page -

i want retreive number of istances of class flat file flat.ser , aim wrote method here reported:

flat.java

public static arraylist<flat> retreiveflat() throws classnotfoundexception, ioexception {      fileinputstream fis = new fileinputstream("path/flat.ser");     objectinputstream ois = new objectinputstream(fis);     flat f;     arraylist<flat> al = new arraylist<flat>();      while (fis.available() > 0) {         object retrieved = ois.readobject();         if(retrieved instanceof flat) {             f = (flat) retrieved;             if(f.gettypeofflat().equals("double")) {                 al.add(f);             }         }     }     ois.close();     return al; } 

the method used in jsp page:

page.jsp

<%@ page language="java" contenttype="text/html; charset=iso-8859-1" pageencoding="iso-8859-1"%> <%@ page import="entity.flat" %> <%@ page import="java.util.*" %> <%     arraylist<flat> al = new arraylist<flat>();     al = flat.retreiveflat();     int = 0;     while(al.get(i) != null){       //do        i++;}%> 

the problem istance of al empty in jsp page though have assigned return of method retreiveflat() , though in debug mode see inside body of retreiveflat() method list not empty. exception of type indexoutofboundsexception when call get() method on al. tell me make mistake?

i don't know why list empty, attempt iterate on list indeed throw indexoutofboundsexception. should use for-each loop (also called enhanced for).

replace

while(al.get(i) != null){     // al.get(i) i++;} 

with this:

for(flat flat : al) {     // flat }