SharedLink object is coming null for my shared file !

BoxFolder folder = new BoxFolder(api, innerItemInfo.getID());
//folder.getItemURL();
Iterator itemInfoItr = folder.iterator();
while(itemInfoItr.hasNext()) {
BoxItem.Info folderItemInfo = itemInfoItr.next();
BoxSharedLink boxSharedLink = folderItemInfo.getSharedLink();
System.out.println("\t\t" +folderItemInfo.getName());
if(boxSharedLink != null){
System.out.println("\t\t" +boxSharedLink.getUnsharedDate());
}

}