Sean Owen <srowen <at> gmail.com> writes:
>
> It throws an exception except in a few implementations, mostly the
> ones based on a database. It isn't something that's really used -- you
> instead update the backing store indirectly. Yes, the model is batch
> re-reads of data once in a while. Updates are not in real time in this
> model.
Hi Sean:
I write an implementation of GenericDataModel , to make
setPreference and removePreference methods be able to update the data in memory
in real time way. Here is the code below,correct me if I am wrong.
public synchronized void setPreference(long userID, long itemID, float value)
{
if(!this.isUserExist(userID) || !this.isItemExist(itemID))
{
throw new UnsupportedOperationException();
}
if(!preferenceFromUsers.containsKey(userID))
{
List<Preference> currentPrefs = Lists.newArrayList();
currentPrefs.add(new GenericPreference(userID,
itemID, value));
PreferenceArray preferenceArray = new
GenericUserPreferenceArray(currentPrefs);
preferenceFromUsers.put(userID,preferenceArray);
}
else
{
PreferenceArray preferenceFromUser =
preferenceFromUsers.get(userID);
if(preferenceFromUser.hasPrefWithItemID(itemID))
{
for(Preference p:preferenceFromUser)
{
if(p.getItemID()==itemID)
{
p.setValue(value);
break;
}
}
}else
{
List<Preference> currentPrefs =
Lists.newArrayList();
for(Preference p:preferenceFromUser)
{
currentPrefs.add(new
GenericPreference(p.getUserID(), p.getItemID(), p.getValue()));
}
currentPrefs.add(new
GenericPreference(userID, itemID, value));
PreferenceArray preferenceArray = new
GenericUserPreferenceArray(currentPrefs);
preferenceFromUsers.put(userID,preferenceArray);
}
}
//same as construction method of GenericDataModel
this.refreshGenericDataModelCustom(preferenceFromUsers, null);
}
public synchronized boolean isUserExist(long userID)
{
boolean flag = false;
for(long userIdTmp:userIDs)
{
if(userIdTmp==userID)
{
flag = true;
break;
}
}
return flag;
}
public synchronized boolean isItemExist(long itemID)
{
boolean flag = false;
for(long itemIDTmp:itemIDs)
{
if(itemIDTmp==itemID)
{
flag = true;
break;
}
}
return flag;
}
