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Limit uses of a function in a period of time (android)

I want to limit the calls to a function within one day.
The problem is I'm a bit confused of how to use the Date and Calendar classes...
private int usesLeft //Set every day to the number of uses
private void function() {
if(usesLeft > 0) {
//Function's body...
}
usesLeft--;
}
I need to find out when a new day starts in order to reset the usesLeft variable.

Well I found a solution...
The better side of this solution is that the user can't "cheat" because then he'll lose activity days (If my analysis of the code behavior is right).
if(lastDayActive < (int)Math.floor(System.currentTimeMillis()/86400000)) {
usesLeft = 100;
//Initializes the day value
lastDayActive = (int)Math.floor(System.currentTimeMillis()/86400000);
}
If there's any way to prevent the user from manually changing the date and therefore gaining more uses I'd really like to hear about it.

How to determine if the specific time is between given range?

Problem: I have a list containg hours, for example:
08:15:00
08:45:00
09:00:00
12:00:00
...
application is allowing user to make an appointment for a specific hour let'say: 8:15:00, each meeting takes half an hour.
Question: How to determine if there is a slot needed for appointment like this? I know that Calendar class have methods before() nad after(), but it doesn'solve my problem. I mean if there is appointment at 12:00 and another one at 12:00, how to prevent before making another one at 12:15?
edit:
I've tried using methods I mentioned before, like:
Calendar cal1 = Calendar.getInstance(); // for example 12:00:00
Calendar cal2 = Calendar.getInstance(); // for exmaple 12:30:00
Calendar userTime = Calendar.getInstance(); // time to test: 12:15:00
if(user.after(cal1)&& user.before(cal2)){
... // do sth
}

Check if the date to check is between the two provided:
SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy hh:mm");
Date before = sdf.parse("07/05/2012 08:00");
Date after = sdf.parse("07/05/2012 08:30");
Date toCheck = sdf.parse("07/05/2012 08:15");
//is toCheck between the two?
boolean isAvailable = (before.getTime() < toCheck.getTime()) && after.getTime() > toCheck.getTime();
To book for a determinate hour, I would do a class with two dates and a method to check this:
public class Appointment{
private Date start;
private Date end;
public boolean isBetween(Date toCheck){....}
}
Then you can simply do an Schedule class extending ArrayList, adding a method isDateAvailable(Date toCheck), iterating the list of Appointments and checking that there is no one conflicting.

I'd have some kind of appointment class with either a start timestamp and a duration or a start time and an end time. Then when adding new appointments to the schedule, check that the appointment with the start time before the new appointment doesn't run over the start time of the proposed new appointment.

Well how you would do it specifically depends on how you are storing your data, format, etc., but generally what you would do is simply check if there is an appointment for any time between the requested time to the requested time + requested length.
// Example (using int time(1 = 1 minute), assuming that appointments can only be at 15min intervals)
boolean isHalfHourTimeSlotAvaliable(int time) {
for (int i = 0; i < appointments.size(); i++) {
if (appointments.get(i).time == time || appointments.get(i).time == time + 15) {
return false;
}
}
return true;
}

Parsing a List<List<String>> in Android?

I'm developing a custom Adsense report tool using Google Java Client Library for Android. I've successfully authenticated and can make API calls to the server. but now when I receive the response, I don't know how to parse it and correctly show the result to user.
According to the javaDocs, AdsenseReportsGenerateResponse.getRows() generates a List> But I'm kinda lost how to properly parse it to get:
-Today's earnings
-Yesterday's earnings
-Last 7 days
-Last month
-From the beginning of time
Here's part of my code related to the question
Reports.Generate request = adsense.reports().generate(startDate, endDate);
request.setMetric(Arrays.asList("PAGE_VIEWS", "AD_REQUESTS", "AD_REQUESTS_COVERAGE", "CLICKS",
"AD_REQUESTS_CTR", "COST_PER_CLICK", "AD_REQUESTS_RPM", "EARNINGS"));
request.setDimension(Arrays.asList("DATE", "WEEK", "MONTH"));
request.setSort(Arrays.asList("+DATE"));
AdsenseReportsGenerateResponse response = request.execute();
//TODO: Here be dragons
response.getRows();
Edit: Here is the javaDoc which mentions the getRow()
Hmm it seems nobody on this site can help?!

You should find our sample code useful: http://code.google.com/p/google-api-java-client/wiki/APIs#AdSense_Management_API
Namely, this is the file you're interested in: http://code.google.com/p/google-api-java-client/source/browse/adsense-cmdline-sample/src/main/java/com/google/api/services/samples/adsense/cmdline/GenerateReport.java?repo=samples
Here's a snippet of code to print the output. Mind you, this is for a command line application, but should be easily adaptable:
if ((response.getRows() != null) && !response.getRows().isEmpty()) {
// Display headers.
for (AdsenseReportsGenerateResponseHeaders header : response.getHeaders()) {
System.out.printf("%25s", header.getName());
}
System.out.println();
// Display results.
for (List<String> row : response.getRows()) {
for (String column : row) {
System.out.printf("%25s", column);
}
System.out.println();
}
System.out.println();
} else {
System.out.println("No rows returned.");
}
As for getting the data for different periods of time, you should probably be running different reports, not cramming it all into one, as that would take different start dates and end dates. Here's how it works:
Today's earnings: set the start and end dates to today, set the dimension list to just DATE
Yesterday's earnings: set the start and end date to yesterday, set the dimension list to just DATE
Last 7 days: if you want data per day, then you set the start date to 7 days ago, the end date to today, and the dimension list to just DATE. If you want to aggregate the stats, you may need to calculate this yourself, as WEEK and MONTH refer to a calendar week and month, not the last 7 days.
Last month: start date 1st of last month, end date last day of the month, dimension MONTH.
All time: how do you want this aggregated? Per month? Then set the start date to, say, 1980-1-1, end date to today and dimension to MONTH.
This blog post should help with understanding reporting concepts a bit better: http://adsenseapi.blogspot.com/2011/11/adsense-management-api-diving-into.html
Let me know if you need help with anything else!

Its not a List<List> as far as I understand the api. Try this:
String[][] array = response.getRows();
for (int i = 0; i < array.getSize(); i++){
String dimension = array[i][0];
String metric = array[i][1];
//Do what you want with them
}
I am writing this because the API says it has a list of dimensions with one value for the string and one for the metric, as far as I understand.
If you expect several cells on each row (Which I believe the API doesn't work that way), you need to add another for inside and get the size of the current list probably with something like array[i].getSize()
Post back if it doesn't help you.
Edit: I see now. Try this:
List list = response.getRows();
for (int i = 0; i < list.size(); i++){
List<String> list2 = list.get(i);
for (int j = 0; j < list2.size(); j++){
String value = list2.get(j);
//Do what you want
}
}

Grouping objects by date: am I an idiot?

I have a list of objects called Activity:
class Activity {
public Date activityDate;
public double amount;
}
I want to iterate through List, group them by date and return a new list . Here's what I currently do:
private List<Activity> groupToList(List<Activity> activityList) {
SimpleDateFormatter sdf = new SimpleDateFormatter("YYYY-MM-DD");
Map<String,Activity> groupMap = new HashMap<String,Activity>();
for (Activity a in activityList) {
String key = sdf.format(a.getActivityDate());
Activity group = groupMap.get(key);
if (group == null) {
group = new Activity();
groupMap.add(key, group);
}
group.setAmount(group.getAmount() + a.getAmount());
}
return new ArrayList<Activity>(groupMap.values());
}
Is it a WTF to use the DateFormatter in this way?
I'm using the DateFormatter because each activityDate could have time information.

I would just use the date object itself as the key. If it it bothers you because the date object is mutable, then use its toString() value. No reason to go making formats.
If the issue is that you want to normalize the date by removing the time component, it would be much better to do that withing the Activity object and remove the time component. If the issue is still further that there are potential time zone issues, I would use JodaTime, but there is no object in the JDK currently that represents a pure date without time, so going with a string isn't outrageous, but it should be hidden behind a method in the Activity object and the fact that it is a date formatted string without a time component should be an implementation detail.

java.util.Date is a quite poor abstraction for your need; it is IMO fair to stick to strings if nothing better is around, HOWEVER Joda-time provides a good datatype for you: DateMidnight or alternatively LocalDate if Activity is strictly timezome-independant.
other than that, the code looks good to me, you might be able to shorten it a bit using an implementation of Multimap, to avoid messy null-checking code. to be honest, it doesn't get much shorter than your solution:
public List<Activity> groupedByDate(List<Activity> input) {
//group by day
final Multimap<DateMidnight, Activity> activityByDay
= Multimaps.index(input, new Function<Activity, DateMidnight>() {
#Override
public DateMidnight apply(Activity from) {
return new DateMidnight(from.activityDate);
}
});
//for each day, sum up amount
List<Activity> ret = Lists.newArrayList();
for (DateMidnight day : activityByDay.keySet()) {
Activity ins = new Activity();
ins.activityDate = day.toDate();
for (Activity activity : activityByDay.get(day)) {
ins.amount+=activity.amount;
}
}
return ret;
}

Why not simply create a HashMap<Date, Activity>() instead of the roundabout way with Strings?
Sorry, I didn't answer the question. The answer is: yes, unless I am an idiot ;)

You could do this using the Date as the key if you used a TreeMap and provided a Comparator that only compared the year, month and day and not the time.

As already mentioned the best solution is to represent your date with day precission. If this is not possible joda is nice library.
If you can ignore daylight saving time then grouping by date can be accomplished much easier. A unix time day is 86 400 s long. The timestamp does ignore leap seconds. (Your timer stops for one second or the leap second is distributed in some way.) All date values were day is equal are the same day:
int msPerDay = 86400 * 1000;
long day = new Date().getTime() / msPerDay
One minor point is to adjust the timezone. For my timezone CET (UTC/GMT +1 hour) the GMT day starts one our later:
new GregorianCalendar(2009, 10, 1, 1, 0).getTime().getTime() / msPerDay) ==
new GregorianCalendar(2009, 10, 2, 0, 59).getTime().getTime() / msPerDay) ==
new Date().getTime() / msPerDay
If the daylight saving time is significant the best way is to use joda. The rules are just to complicated and locale specific to implement.

Can anyone help with a java problem regarding date properties?

I basically want to say
if the date is unchanged run this alert
my date field is set up like this
StartDate = new DateField("Start Date ", DateField.DATE);
cal1 = Calendar.getInstance();
cal1.set(Calendar.YEAR, 2009);
cal1.set(Calendar.MONTH, 3);
cal1.set(Calendar.DAY_OF_MONTH, 1);
StartDate.setDate(cal1.getTime());
and i have this but i am not sure where to begin to make it right.
if(StartDate.equals(Calendar.DAY_OF_MONTH, 1))
{
AlertNameNotEntered.setString("Please select a Start Date");
mDisplay.setCurrent(AlertNameNotEntered);
}
Thanks

I assume you want something like this:
if(StartDate.getDate().getTime() == cal1.getTime()) // Date is unchanged
{
AlertNameNotEntered.setString("Please select a Start Date");
mDisplay.setCurrent(AlertNameNotEntered);
}

It seems to me you have quite a few gaps in your knowledge regarding basic Java. There are no short-cuts to getting to know the language and the standard library. Consult javadocs for Calendar, Date and DateField classes.