Develop Reference

check if saved date is one day before to current date android

Okay so i read this : Check date with todays date
#sudocode gave this code :
Calendar c = Calendar.getInstance();
// set the calendar to start of today
c.set(Calendar.HOUR_OF_DAY, 0);
c.set(Calendar.MINUTE, 0);
c.set(Calendar.SECOND, 0);
c.set(Calendar.MILLISECOND, 0);
// and get that as a Date
Date today = c.getTime();
// or as a timestamp in milliseconds
long todayInMillis = c.getTimeInMillis();
// user-specified date which you are testing
// let's say the components come from a form or something
int year = 2011;
int month = 5;
int dayOfMonth = 20;
// reuse the calendar to set user specified date
c.set(Calendar.YEAR, year);
c.set(Calendar.MONTH, month);
c.set(Calendar.DAY_OF_MONTH, dayOfMonth);
// and get that as a Date
Date dateSpecified = c.getTime();
// test your condition
if (dateSpecified.before(today)) {
System.err.println("Date specified [" + dateSpecified + "] is before today [" + today + "]");
} else {
System.err.println("Date specified [" + dateSpecified + "] is NOT before today [" + today + "]");
}
But imagine the saved date was 28/01/2018 11:00pm and i run this at 28/01/2018 11:15pm so this code will tell me that saved date is before the current date.
What i want is, the code should only run a function if the saved date is more than one day old... (not 24 hours but actually a day or more old) lets say saved date it 27/01/2018 11:00pm and current date is 28/01/2018 then it should run.. how do i implement this ?

You can do something like this:
public long daysBetween(Calendar first, Calendar second) {
long diffInMillis = second.getTimeInMillis() - first.getTimeInMillis();
return TimeUnit.MILLISECONDS.toDays(diffInMillis);
}
And then just ask if the difference is >= 1. This also assumes that second >= first.
This example is using the standard Java (7) date stuff, so you should be able to use it in your project.

tl;dr
Determining dates requires a time zone.
Use only java.time classes, never legacy java.util.Date, Calendar, java.sql.Date, java.sql.Timestamp, etc.
myResultSet.getObject(
… ,
Instant.class
) // Retrieve a `java.time.Instant` from a column of type akin to the SQL-standard `TIMESTAMP WITH TIME ZONE`.
.atZone(
ZoneId.of( "Pacific/Auckland" )
)
.toLocalDate()
.isEqual(
LocalDate.now( ZoneId.of( "Pacific/Auckland" ) )
)
Avoid legacy date-time classes
The terrible Date and Calendar legacy classes were supplanted years ago by the modern java.time classes.
Time zones
Your Question ignores the crucial issue of time zone. For any given moment, the date and time-of-day both vary around the globe by time zone. You cannot talk about dates without talking about time zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.
If no time zone is specified, the JVM implicitly applies its current default time zone. That default may change at any moment during runtime(!), so your results may vary. Better to specify your [desired/expected time zone][2] explicitly as an argument.
Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "America/Montreal" ) ;
LocalDate today = LocalDate.now( z ) ;
If you want to use the JVM’s current default time zone, ask for it and pass as an argument. If omitted, the JVM’s current default is applied implicitly. Better to be explicit, as the default may be changed at any moment during runtime by any code in any thread of any app within the JVM.
ZoneId z = ZoneId.systemDefault() ; // Get JVM’s current default time zone.
Or specify a date. You may set the month by a number, with sane numbering 1-12 for January-December.
LocalDate ld = LocalDate.of( 1986 , 2 , 23 ) ; // Years use sane direct numbering (1986 means year 1986). Months use sane numbering, 1-12 for January-December.
Or, better, use the Month enum objects pre-defined, one for each month of the year. Tip: Use these Month objects throughout your codebase rather than a mere integer number to make your code more self-documenting, ensure valid values, and provide type-safety.
LocalDate ld = LocalDate.of( 1986 , Month.FEBRUARY , 23 ) ;
Never assume 00:00:00
Also, do not assume the day starts at 00:00:00. Because of anomalies such as Daylight Saving Time (DST), the day may start at another time, such as 01:00:00. Let java.time determine the first moment of the day. Specify a time zone to yield a ZonedDateTime object representing a specific moment.
ZonedDateTime startOfToday = LocalDate.now( z ).atStartOfDay( z ) ;
ZonedDateTime startOfYesterday = startOfToday.toLocalDate().minusDays( 1 ).atStartOfDay( z ) ;
For querying database, it is often best to use UTC values. To adjust from our time zone to UTC, simply extract a Instant.
Instant start = startOfToday.toInstant() ;
Instant stop = startOfYesterday.toInstant() ;
Ready to query database. Using Half-Open approach here where beginning is inclusive while ending is exclusive. So, do not use SQL BETWEEN.
// SQL for SELECT WHERE when_field >= ? AND when_field < ?
myPreparedStatement.setObject( 1 , start ) ;
myPreparedStatement.setObject( 2 , stop ) ;
Comparing dates
If you just want to check the age of a retrieved moment, retrieve an Instant.
Instant instant = myResultSet.getObject( … , Instant.class ) ;
Apply a time zone to get a ZonedDateTime. Then extract the date-only value.
ZonedDateTime zdt = instant.atZone( z ) ;
LocalDate ld = zdt.toLocalDate() ; // Extract the date-only value.
Compare to today's date.
LocalDate yesterday = LocalDate.now( z ).minusDays( 1 ) ; // Subtract one day from today to get yesterday.
Boolean retrievedDateIsYesterday = ld.isEqual( yesterday ) ;
If you work much with spans-of-time, see the Interval and LocalDateRange classes in the ThreeTen-Extra project linked below.
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Samsung J7 returning first day of week as 2

I have written a code for custom calendar where I am using calendar object.I have used the method getFirstDayOfWeek() to retrieve first day of every month.On loading every month the method "_calendar.getTime()" returns the first date. On every device it is returning correctly.But on samsung J7 it returns starting date of week as 2 . Here is my debugger log for samsung J7
java.util.GregorianCalendar[time=?,areFieldsSet=false,lenient=true,zone=Asia/Calcutta,firstDayOfWeek=2,minimalDaysInFirstWeek=4,ERA=1,YEAR=2016,MONTH=10,WEEK_OF_YEAR=41,WEEK_OF_MONTH=3,DAY_OF_MONTH=14,DAY_OF_YEAR=288,DAY_OF_WEEK=6,DAY_OF_WEEK_IN_MONTH=2,AM_PM=1,HOUR=3,HOUR_OF_DAY=15,MINUTE=46,SECOND=58,MILLISECOND=199,ZONE_OFFSET=19800000,DST_OFFSET=0]
It says firstDayOfWeek = 2 , for rest of the devices it shows as 1. So any ideas for the solution?
Thanks.

Ok, I got the solution. Instead of using getFirstDayOfWeek() I passed 1 as parameter. So its working properly now.
_calendar.set(year, (month - 1), 1);
in place of
_calendar.set(year, (month - 1), _calendar.getFirstDayOfWeek());

tl;dr
You seem to conflate first-of-month with first-day-of-week.
The 2 is a hard-coded constant representing Monday.
Apparently your current default locale considers Monday to be the first day of the week.
Use java.time instead.
For first day of the week:
LocalDate.now( ZoneId.of( "America/Montreal" ) )
.with( TemporalAdjusters.previousOrSame( DayOfWeek.MONDAY ) )
For first day of the month:
LocalDate.now( ZoneId.of( "Pacific/Auckland" ) )
.with( ChronoField.DAY_OF_MONTH , 1L )
Details
getFirstDayOfWeek() to retrieve first day of every month
You seem to be confusing first of the week with first of the month.
The first of the month is always 1 of course.
The first of the week is a day-of-week such as Sunday or Monday etc. The definition of the first day of the week in the Calendar class varies, depending on the Locale. For example, in much of North America, the first day is Sunday commonly. In much of Europe, the first day of the week is Monday.
If you fail to specify a Locale, the Calendar class implicitly applies the JVM’s current default locale. Apparently in your default locale the first day of the week is Monday. I deduce that because you report the number 2. If you explore the int constant Calendar.MONDAY, you find it is indeed a primitive int of value 2.
Avoid legacy date-time classes
The Calendar class has many poor design decisions. I consider this varying definition of day-of-week to be one of them. One of many reasons to avoid these troublesome old date-time classes such as Calendar and Date. These classes are now legacy, supplanted by the java.time classes.
Using java.time
The LocalDate class represents a date-only value without time-of-day and without time zone.
A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.
Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "America/Montreal" );
LocalDate today = LocalDate.now( z );
To get the first day of the week, (a) decide what is the first day of the week for you, (b) use a TemporalAdjuster implementation defined in TemporalAdjusters to get the date for a specific DayOfWeek enum object.
DayOfWeek firstDow = DayOfWeek.MONDAY ;
LocalDate ld = today.with( TemporalAdjusters.previousOrSame( firstDow ) ) ;
To get a LocalDate for a certain day of month, call the with method and pass an enum object from ChronoField.DAY_OF_MONTH.
LocalDate firstOfMonth = today.with( ChronoField.DAY_OF_MONTH , 1L ) ;
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
See How to use ThreeTenABP….

Calendar set DAY_OF_WEEK not correct

Hi i have some problem with DAY_OF_WEEK. After research but don't know why.
Input date is :
30/01/2016 - SATURDAY
After run :
calendar.set(Calendar.DAY_OF_WEEK, Calendar.SATURDAY);
Output :
31/01/2016 - SUNDAY(Wrong).
I want it must 30/01/2016 - SATURDAY,
Please help me ?

try by passing Date
Calendar calendar = Calendar.getInstance;
calendar.set(2016, Calendar.JANUARY, 30);
or try this too
Calendar c = Calendar.getInstance();
c.set(Calendar.DAY_OF_WEEK, Calendar.SATURDAY);
for(int i=0; i<7; i++)
{
System.out.print("Start Date : " + c.getTime() + ", ");
c.add(Calendar.DAY_OF_WEEK, 6);
}

tl;dr
LocalDate.of( 2016 , Month.JANUARY , 30 )
.with( TemporalAdjusters.next( DayOfWeek.SATURDAY ) )
2016-02-06
java.time
The modern approach uses java.time classes rather than the troublesome old Calendar class that is now legacy.
LocalDate
The LocalDate class represents a date-only value without time-of-day and without time zone.
A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.
If no time zone is specified, the JVM implicitly applies its current default time zone. That default may change at any moment, so your results may vary. Better to specify your desired/expected time zone explicitly as an argument.
Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "America/Montreal" ) ;
LocalDate today = LocalDate.now( z ) ;
If you want to use the JVM’s current default time zone, ask for it and pass as an argument. If omitted, the JVM’s current default is applied implicitly. Better to be explicit, as the default may be changed at any moment during runtime by any code in any thread of any app within the JVM.
ZoneId z = ZoneId.systemDefault() ; // Get JVM’s current default time zone.
Or specify a date. You may set the month by a number, with sane numbering 1-12 for January-December.
LocalDate ld = LocalDate.of( 1986 , 2 , 23 ) ; // Years use sane direct numbering (1986 means year 1986). Months use sane numbering, 1-12 for January-December.
Or, better, use the Month enum objects pre-defined, one for each month of the year. Tip: Use these Month objects throughout your codebase rather than a mere integer number to make your code more self-documenting, ensure valid values, and provide type-safety.
LocalDate ld = LocalDate.of( 1986 , Month.FEBRUARY , 23 ) ;
Adjuster
To move from one date to another, use a TemporalAdjuster implementation found in TemporalAdjusters class. Specify the desired day-of-week using [DayOfWeek][2] enum.
LocalDate previousOrSameMonday = today.with( TemporalAdjusters.previousOrSame( DayOfWeek.SATURDAY ) ) ;
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….

Days of the week on Android

I'm working on an Android app where I need to display the days of the week from the calendar. Can I do that using the calendar API ? or there is a library that can I use ?
Thanks

For date handling in Android, I recommend 310ABP, a port of the Java 8 new date APIs for Android.

Use Calendar object to get these things done.

You could use the JodaTime library to display the current day of the week.
LocalDate newDate = new LocalDate();
int dayOfWeek = newDate.getDayOfWeek();

or there is a library that can I use ?
Yes. Use the back-port of the java.time classes. See "Android" item below.
Using java.time
LocalDate
The LocalDate class represents a date-only value without time-of-day and without time zone.
A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.
Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "America/Montreal" );
LocalDate today = LocalDate.now( z );
TemporalAdjuster
To get the first day of the week, (a) decide what is the first day of the week for you, (b) use a TemporalAdjuster implementation defined in TemporalAdjusters to get the date for a specific [DayOfWeek][6] enum object.
LocalDate ld = today.with( TemporalAdjusters.previousOrSame( DayOfWeek.MONDAY ) ) ;
To get a week’s worth of dates, add a day at a time.
LocalDate localDate = ld ; // Initialize our looping variable.
List<LocalDate> dates = new ArrayList<>( 7 ) ;
for( int i = 0 , i < 7 , i ++ ) { // Loop seven times, to cover a week.
localDate = localDate.plusDays( i );
dates.add( localDate ) ;
}
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
See How to use ThreeTenABP….

How to get localization of day in week

I couldnt find a symbol for that in SimpleDateFormat
How can I get the current day's localized name?
For example: Monday: 1. day of week ; Tuesday: 2.day, wednesday:3.day .....
I want to get Presentation Number "1" instead of Monday ...

As per other questions, you don't need SimpleDateFormat to get the numeric day of the week - that is provided by Calendar directly via the DAY_OF_WEEK field (which goes from 1 to 7 where 1 is SUNDAY and 7 is SATURDAY):
Calendar today = Calendar.getInstance();
int dayOfWeek = today.get(Calendar.DAY_OF_WEEK);
// Day of Week is a number between 1 and 7 where 1 is Sunday.
int dayOfWeekMondayFirst = (dayOfWeek + 5) % 7 + 1;

tl;dr
For the number 1-7, meaning Monday-Sunday, for today:
LocalDate.now().getDayOfWeek().getValue()
For the localized name of the day of the week:
LocalDate // Represent a date-only, without time-of-day and without time zone.
.now( // Get today’s current date as seen in the wall-clock time used by the people of a particular region (a time zone).
ZoneId.of( "Africa/Tunis" ) // Specify time zone.
) // Returns a `LocalDate`.
.getDayOfWeek() // Returns one of seven `DayOfWeek` enum objects.
.getDisplayName( // Localize the name of the day-of-week.
TextStyle.FULL , // How long or abbreviated should the localized string be.
Locale.UK // Specify a `Locale` to determine the human language and cultural norms to use in localizing.
) // Returns a string.
Monday
java.time
The modern approach uses the java.time classes that long ago supplanted the terrible legacy date-time classes such as SimpleDateFormat.
To get the day-of-week today, we need the date.
LocalDate
The LocalDate class represents a date-only value without time-of-day and without time zone or offset-from-UTC.
A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.
If no time zone is specified, the JVM implicitly applies its current default time zone. That default may change at any moment during runtime(!), so your results may vary. Better to specify your desired/expected time zone explicitly as an argument.
Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 2-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "America/Montreal" ) ;
LocalDate today = LocalDate.now( z ) ;
If you want to use the JVM’s current default time zone, ask for it and pass as an argument. If omitted, the JVM’s current default is applied implicitly. Better to be explicit, as the default may be changed at any moment during runtime by any code in any thread of any app within the JVM.
ZoneId z = ZoneId.systemDefault() ; // Get JVM’s current default time zone.
DayOfWeek
The DayOfWeek enum pre-defines a set of seven objects, one for each day of the week.
Ask the LocalDate object for its DayOfWeek.
DayOfWeek dow = ld.getDayOfWeek() ;
Ask the DayOfWeek object to automatically localize its name. The DayOfWeek::getDisplayName method translates the name of the day into any human language specified by a Locale such as Locale.US or Locale.CANADA_FRENCH.
String output = dow.getDisplayName( TextStyle.FULL , Locale.CANADA_FRENCH );
lundi
Or, in US English.
String output = dow.getDisplayName( TextStyle.FULL , Locale.US );
Monday
To get the number of the day-of-week, where Monday-Sunday is 1-7 per the ISO 8601 standard, ask the DayOfWeek enum object for its value.
int dowNumber = dow.getValue() ; // 1-7 for Monday-Sunday.
To get the number 1-7 as part of a larger formatting pattern use e or c as directed in the DateTimeFormatter class.
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.