Convert from Long to date format

java.util.Date dateObj = new java.util.Date(timeStamp);

Here timeStamp is your long integer which is actually timestamp in millieseconds, you get the java date object, now you can convert it into string by this

SimpleDateFormat dateformatYYYYMMDD = new SimpleDateFormat("yyyyMMdd");
SimpleDateFormat dateformatMMDDYYYY = new SimpleDateFormat("MMddyyyy");

StringBuilder nowYYYYMMDD = new StringBuilder( dateformatYYYYMMDD.format( dateObj ) );
StringBuilder nowMMDDYYYY = new StringBuilder( dateformatMMDDYYYY.format( dateObj ) );

You can use below line of code to do this. Here timeInMilliSecond is long value.

 String dateString = new SimpleDateFormat("MM/dd/yyyy").format(new Date(TimeinMilliSeccond));

Or you can use below code too also.

 String longV = "1343805819061";
 long millisecond = Long.parseLong(longV);
 // or you already have long value of date, use this instead of milliseconds variable.
 String dateString = DateFormat.format("MM/dd/yyyy", new Date(millisecond)).toString();

Reference:- DateFormat and SimpleDateFormat

P.S. Change date format according to your need.

java.time and ThreeTenABP

I am providing the modern answer. I suggest using java.time, the modern Java date and time API, for your date work. This will work on your Android version:

    // Take Catalan locale as an example for the demonstration
    DateTimeFormatter dateFormatter
            = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM)
                    .withLocale(Locale.forLanguageTag("ca"));

    long millisecondsSinceEpoch = 1_343_805_819_061L;
    ZonedDateTime dateTime = Instant.ofEpochMilli(millisecondsSinceEpoch)
            .atZone(ZoneId.systemDefault());
    String dateString = dateTime.format(dateFormatter);
    System.out.println("As formatted date: " + dateString);

Output is:

As formatted date: 01/08/2012

I recommend that you use a built-in localized date format for presentation to your user. I took Catalan date format just as an example. Formats for many languages, countries and dialects are built-in.

The SimpleDateFormat class used in most of the old answers is a notorious troublemaker of a class. The Date class also used is poorly designed too. Fortunately they are both long outdated. It’s no longer recommended to use any of those. And I just find java.time so much nicer to work with.

Question: Doesn’t java.time require Android API level 26?

java.time works nicely on both older and newer Android devices. It just requires at least Java 6.

• In Java 8 and later and on newer Android devices (from API level 26) the modern API comes built-in.
• In non-Android Java 6 and 7 get the ThreeTen Backport, the backport of the modern classes (ThreeTen for JSR 310; see the links at the bottom).
• On (older) Android use the Android edition of ThreeTen Backport. It’s called ThreeTenABP. And make sure you import the date and time classes from org.threeten.bp with subpackages.

Links

• Oracle tutorial: Date Time explaining how to use java.time.
• Java Specification Request (JSR) 310, where java.time was first described.
• ThreeTen Backport project, the backport of java.time to Java 6 and 7 (ThreeTen for JSR-310).
• ThreeTenABP, Android edition of ThreeTen Backport
• Question: How to use ThreeTenABP in Android Project, with a very thorough explanation.

You can use method setTime on the Date instance or the contructor Date(long);

setTime(long time) 
      Sets this Date object to represent a point in time that is time milliseconds after January 1, 1970 00:00:00 GMT.

Date(long date) 
      Allocates a Date object and initializes it to represent the specified number of milliseconds since the standard base time known as "the epoch", namely January 1, 1970, 00:00:00 GMT

Then use the simple date formater

see http://docs.oracle.com/javase/1.4.2/docs/api/javax/swing/text/DateFormatter.html