[Chapter 16] DateFormat

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| Chapter 16 The java.text Package |

# DateFormat

## Name

DateFormat

## Synopsis

Class Name:

  `java.text.DateFormat`

Superclass:

  `java.text.Format`

Immediate Subclasses:

  `java.text.SimpleDateFormat`

Interfaces Implemented:

  `java.lang.Cloneable`

Availability:

  New as of JDK 1.1

## Description

The `DateFormat` class formats and parses dates and times in a locale-specific manner. `DateFormat` is an `abstract` class, but it provides factory methods that return useful instances of `DateFormat` subclasses. These factory methods come in three groups:

- The `getDateInstance()` methods return objects that format and parse only dates.

- The `getDateTimeInstance()` methods return objects that format and parse date and time combinations.

- The `getTimeInstance()` methods return objects that format only times.

Certain of these factory methods allow you to specify the style, or length, of the resulting date and time strings. The interpretation of the style parameter is locale-specific. For the locale `Locale.US`, the styles and their results are as follows:

`FULL`

  `Tuesday, March 04, 1997 12:00:00 o'clock AM EST`

`LONG`

  `March 04, 1997 12:00:00 AM EST`

`MEDIUM`

  `04-Mar-97 12:00:00 AM`

`SHORT`

  `3/4/97 12:00 AM`

There is also a `DEFAULT` style, which is equivalent to `MEDIUM`.

The `DateFormat` class defines a number of field constants that represent the various fields in formatted date and time strings. These field constants can create `FieldPosition` objects.

## Class Summary

    public abstract class java.text.DateFormat extends java.text.Format
                          implements java.lang.Cloneable {
      // Constants
      public static final int AM_PM_FIELD;
      public static final int DATE_FIELD;
      public static final int DAY_OF_WEEK_FIELD;
      public static final int DAY_OF_WEEK_IN_MONTH_FIELD;
      public static final int DAY_OF_YEAR_FIELD;
      public static final int DEFAULT;
      public static final int ERA_FIELD;
      public static final int FULL;
      public static final int HOUR0_FIELD;
      public static final int HOUR1_FIELD;
      public static final int HOUR_OF_DAY0_FIELD;
      public static final int HOUR_OF_DAY1_FIELD;
      public static final int LONG;
      public static final int MEDIUM;
      public static final int MILLISECOND_FIELD;
      public static final int MINUTE_FIELD;
      public static final int MONTH_FIELD;
      public static final int SECOND_FIELD;
      public static final int SHORT;
      public static final int TIMEZONE_FIELD;
      public static final int WEEK_OF_MONTH_FIELD;
      public static final int WEEK_OF_YEAR_FIELD;
      public static final int YEAR_FIELD;
      // Variables
      protected Calendar calendar;
      protected NumberFormat numberFormat;
      // Constructors
      protected DateFormat();
      // Class Methods
      public static Locale[] getAvailableLocales();
      public static final DateFormat getDateInstance();
      public static final DateFormat getDateInstance(int style);
      public static final DateFormat getDateInstance(int style, Locale aLocale);
      public static final DateFormat getDateTimeInstance();
      public static final DateFormat getDateTimeInstance(int dateStyle,
                                     int timeStyle);
      public static final DateFormat getDateTimeInstance(int dateStyle,
                                     int timeStyle, Locale aLocale);
      public static final DateFormat getInstance();
      public static final DateFormat getTimeInstance();
      public static final DateFormat getTimeInstance(int style);
      public static final DateFormat getTimeInstance(int style, Locale aLocale);
      // Instance Methods
      public Object clone();
      public boolean equals(Object obj);
      public final String format(Date date);
      public final StringBuffer format(Object obj, StringBuffer toAppendTo,
                                FieldPosition fieldPosition);
      public abstract StringBuffer format(Date date, StringBuffer toAppendTo,
                                   FieldPosition fieldPosition);
      public Calendar getCalendar();
      public NumberFormat getNumberFormat();
      public TimeZone getTimeZone();
      public int hashCode();
      public boolean isLenient();
      public Date parse(String text);
      public abstract Date parse(String text, ParsePosition pos);
      public Object parseObject(String source, ParsePosition pos);
      public void setCalendar(Calendar newCalendar);
      public void setLenient(boolean lenient);
      public void setNumberFormat(NumberFormat newNumberFormat);
      public void setTimeZone(TimeZone zone);
    }

## Constants

### AM_PM_FIELD

#### public final static int AM_PM_FIELD

Description

  A field constant that represents the A.M./P.M. field.

### DATE_FIELD

#### public final static int DATE_FIELD

Description

  A field constant that represents the date (day of month) field.

### DAY_OF_WEEK_FIELD

#### public final static int DAY_OF_WEEK_FIELD

Description

  A field constant that represents the day-of-the-week field.

### DAY_OF_WEEK_IN_MONTH_FIELD

#### public final static int DAY_OF_WEEK_IN_MONTH_FIELD

Description

  A field constant that represents the day of the week in the current month field.

### DAY_OF_YEAR_FIELD

#### public final static int DAY_OF_YEAR_FIELD

Description

  A field constant that represents the day-of-the-year field.

### DEFAULT

#### public final static int DEFAULT

Description

  A constant that specifies the default style.

### ERA_FIELD

#### public final static int ERA_FIELD

Description

  A field constant that represents the era field.

### FULL

#### public final static int FULL

Description

  A constant that specifies the most complete style.

### HOUR0_FIELD

#### public final static int HOUR0_FIELD

Description

  A field constant that represents the zero-based hour field.

### HOUR1_FIELD

#### public final static int HOUR1_FIELD

Description

  A field constant that represents the one-based hour field.

### HOUR_OF_DAY0_FIELD

#### public final static int HOUR_OF_DAY0_FIELD

Description

  A field constant that represents the zero-based hour of the day field.

### HOUR_OF_DAY1_FIELD

#### public final static int HOUR_OF_DAY1_FIELD

Description

  A field constant that represents the one-based hour of the day field.

### LONG

#### public final static int LONG

Description

  A constant that specifies the long style.

### MEDIUM

#### public final static int MEDIUM

Description

  A constant that specifies the medium style.

### MILLISECOND_FIELD

#### public final static int MILLISECOND_FIELD

Description

  A field constant that represents the millisecond field.

### MINUTE_FIELD

#### public final static int MINUTE_FIELD

Description

  A field constant that represents the minute field.

### MONTH_FIELD

#### public final static int MONTH_FIELD

Description

  A field constant that represents the month field.

### SECOND_FIELD

#### public final static int SECOND_FIELD

Description

  A field constant that represents the second field.

### SHORT

#### public final static int SHORT

Description

  A constant that specifies the short style.

### TIMEZONE_FIELD

#### public final static int TIMEZONE_FIELD

Description

  A field constant that represents the time-zone field.

### WEEK_OF_MONTH_FIELD

#### public final static int WEEK_OF_MONTH_FIELD

Description

  A field constant that represents the week-of-the-month field.

### WEEK_OF_YEAR_FIELD

#### public final static int WEEK_OF_YEAR_FIELD

Description

  A field constant that represents the week-of-the-year field.

### YEAR_FIELD

#### public final static int YEAR_FIELD

Description

  A field constant that represents the year field.

## Variables

### calendar

#### protected Calendar calendar

Description

  A `Calendar` object that internally generates the field values for formatting dates and times.

### numberFormat

#### protected NumberFormat numberFormat

Description

  A `NumberFormat` object that internally formats the numbers in dates and times.

## Constructors

### DateFormat

#### protected DateFormat()

Description

  This constructor creates a `DateFormat`.

## Class Methods

### getAvailableLocales

#### public static Locale[] getAvailableLocales()

Returns

  An array of `Locale` objects.

Description

  This method returns an array of the `Locale` objects for which this class can create `DateFormat` objects.

### getDateInstance

#### public static final DateFormat getDateInstance()

Returns

  A `DateFormat` appropriate for the default `Locale` that uses the default style.

Description

  This method creates a `DateFormat` that formats and parses dates in the default locale with the default style.

#### public static final DateFormat getDateInstance(int style)

Parameters

  `style`

    A style constant.

Returns

  A `DateFormat` appropriate for the default `Locale` that uses the given style.

Description

  This method creates a `DateFormat` that formats and parses dates in the default locale with the given style.

####

     public static final DateFormat getDateInstance(int style, Locale aLocale)

Parameters

  `style`

    A style constant.

  `aLocale`

    The `Locale` to use.

Returns

  A `DateFormat` appropriate for the given `Locale` that uses the given style.

Description

  This method creates a `DateFormat` that formats and parses dates in the given locale with the given style.

### getDateTimeInstance

#### public static final DateFormat getDateTimeInstance()

Returns

  A `DateFormat` appropriate for the default `Locale` that uses the default date and time styles.

Description

  This method creates a `DateFormat` that formats and parses dates and times in the default locale with the default date and time styles.

####

     public static final DateFormat getDateTimeInstance(int dateStyle, int timeStyle)

Parameters

  `dateStyle`

    A style constant.

  `timeStyle`

    A style constant.

Returns

  A `DateFormat` appropriate for the default `Locale` that uses the given data and time styles.

Description

  This method creates a `DateFormat` that formats and parses dates and times in the default locale with the given date and time styles.

####

     public static final DateFormat getDateTimeInstance(int dateStyle, int timeStyle, Locale aLocale)

Parameters

  `dateStyle`

    A style constant.

  `timeStyle`

    A style constant.

  `aLocale`

    The `Locale` to use.

Returns

  A `DateFormat` appropriate for the given `Locale` that uses the given date and time styles.

Description

  This method creates a `DateFormat` that formats and parses dates and times in the given locale with the given date and time styles.

### getInstance

#### public static final DateFormat getInstance()

Returns

  A `DateFormat` appropriate for the default `Locale`.

Description

  This method creates a general purpose `DateFormat` by calling `getDateTimeInstance(DateFormat.SHORT,` `DateFormat.SHORT)`.

### getTimeInstance

#### public static final DateFormat getTimeInstance()

Returns

  A `DateFormat` appropriate for the default `Locale` that uses the default style.

Description

  This method creates a `DateFormat` that formats and parses times in the default locale with the default style.

#### public static final DateFormat getTimeInstance(int style)

Parameters

  `style`

    A style constant.

Returns

  A `DateFormat` appropriate for the default `Locale` that uses the given style.

Description

  This method creates a `DateFormat` that formats and parses times in the default locale with the given style.

####

     public static final DateFormat getTimeInstance(int style, Locale aLocale)

Parameters

  `style`

    A style constant.

  `aLocale`

    The `Locale` to use.

Returns

  A `DateFormat` appropriate for the given `Locale` that uses the given style.

Description

  This method creates a `DateFormat` that formats and parses times in the given locale with the given style.

## Instance Methods

### clone

#### public Object clone()

Returns

  A copy of this `DateFormat`.

Overrides

  `Format.clone()`

Description

  This method creates a copy of this `DateFormat` and returns it.

### equals

#### public boolean equals(Object obj)

Parameters

  `obj`

    The object to be compared with this object.

Returns

  `true` if the objects are equal; `false` if they are not.

Overrides

  `Object.equals()`

Description

  This method returns `true` if `obj` is an instance of `DateFormat` and is equivalent to this `DateFormat`.

### format

#### public final String format(Date date)

Parameters

  `date`

    The `Date` object to be formatted.

Returns

  A string that contains a formatted representation of the date.

Description

  This method formats the given date and returns the result as a string.

####

     public final StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition fieldPosition)

Parameters

  `obj`

    The object to be formatted.

  `toAppendTo`

    A `StringBuffer` on which to append the formatted information.

  `fieldPosition`

    A date or time field.

Returns

  The given buffer `toAppendTo` with the formatted representation of the object appended to it.

Overrides

  `Format.format(Object, StringBuffer, FieldPosition)`

Description

  This method formats the given object and appends the result to the given `StringBuffer`. If `fieldPosition` refers to one of the time or date fields, its beginning and ending indices are filled with the beginning and ending positions of the given field in the resulting formatted string.

####

     public abstract StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition)

Parameters

  `date`

    The `Date` object to be formatted.

  `toAppendTo`

    A `StringBuffer` on which to append the formatted information.

  `fieldPosition`

    A date or time field.

Returns

  The given buffer `toAppendTo` with the formatted representation of the date appended to it.

Description

  This method formats the given date and appends the result to the given `StringBuffer`. If `fieldPosition` refers to one of the time or date fields, its beginning and ending indices are filled with the beginning and ending positions of the given field in the resulting formatted string.

### getCalendar

#### public Calendar getCalendar()

Returns

  The internal `Calendar` object of this `DateFormat`.

Description

  This method returns the `Calendar` object that this `DateFormat` uses internally.

### getNumberFormat

#### public NumberFormat getNumberFormat()

Returns

  The internal `NumberFormat` object of this `DateFormat`.

Description

  This method returns the `NumberFormat` object that this `DateFormat` uses internally.

### getTimeZone

#### public TimeZone getTimeZone()

Returns

  The internal `TimeZone` object of this `DateFormat`.

Description

  This method returns the `TimeZone` object that this `DateFormat` uses internally.

### hashCode

#### public int hashCode()

Returns

  A hashcode for this object.

Overrides

  `Object.hashCode()`

Description

  This method returns a hashcode for this `DateFormat`.

### isLenient

#### public boolean isLenient()

Returns

  A `boolean` value that indicates the leniency of this `DateFormat`.

Description

  This method returns the current leniency of this `DateFormat`. A value of `false` indicates that the `DateFormat` throws exceptions when it tries to parse questionable data, while a value of `true` indicates that the `DateFormat` makes its best guess to interpret questionable data. For example, if the `DateFormat` is being lenient, a date such as March 135, 1997 is interpreted as the 135th day after March 1, 1997.

### parse

#### public Date parse(String text) throws ParseException

Parameters

  `text`

    The string to be parsed.

Returns

  The `Date` object represented by the given string.

Throws

  `ParseException`

    If the text cannot be parsed as a date.

Description

  This method parses a date from the given string, starting from the beginning of the string.

#### public abstract Date parse(String text, ParsePosition pos)

Parameters

  `text`

    The string to be parsed.

  `pos`

    A `ParsePosition` object that can specify a position in the string.

Returns

  The `Date` object represented by the text starting at the given position.

Description

  This method parses a date from the given string, starting from the given position. After the string has been parsed, the given `ParsePosition` object is updated so that its index is after the parsed text.

### parseObject

#### public Object parseObject(String source, ParsePosition pos)

Parameters

  `source`

    The string to be parsed.

  `pos`

    A `ParsePosition` object that can specify a position in the string.

Returns

  The object represented by the text starting at the given position.

Overrides

  `Format.parseObject(String, ParsePosition)`

Description

  This method parses a date from the given string, starting from the given position. After the string has been parsed, the given `ParsePosition` object is updated so that its index is after the parsed text.

### setCalendar

#### public void setCalendar(Calendar newCalendar)

Parameters

  `newCalendar`

    The new `Calendar` to use.

Description

  This method sets the `Calendar` that this `DateFormat` uses internally.

### setLenient

#### public void setLenient(boolean lenient)

Parameters

  `lenient`

    A `boolean` value that specifies the leniency of this `DateFormat`.

Description

  This method sets the leniency of this `DateFormat`. A value of `false` specifies that the `DateFormat` throws exceptions when it tries to parse questionable data, while a value of `true` indicates that the `DateFormat` makes its best guess to interpret questionable data. For example, if the `Calendar` is being lenient, a date such as March 135, 1997 is interpreted as the 135th day after March 1, 1997.

### setNumberFormat

#### public void setNumberFormat(NumberFormat newNumberFormat)

Parameters

  `newNumberFormat`

    The new `NumberFormat` to use.

Description

  This method sets the `NumberFormat` that this `DateFormat` uses internally.

### setTimeZone

#### public void setTimeZone(TimeZone zone)

Parameters

  `zone`

    The new `TimeZone` to use.

Description

  This method sets the `TimeZone` that this `DateFormat` uses internally.

## Inherited Methods

Method | Inherited From | Method | Inherited From
--- | --- | --- | ---
`finalize()` | `Object` | `format(Object)` | `Format`
`getClass()` | `Object` | `notify()` | `Object`
`notifyAll()` | `Object` | `parseObject(String)` | `Format`
`toString()` | `Object` | `wait()` | `Object`
`wait(long)` | `Object` | `wait(long, int)` | `Object`

## See Also

`Calendar`, `Cloneable`, `Date`, `FieldPosition`, `Format`, `Locale`, `NumberFormat`, `ParsePosition`, `String`, `StringBuffer`, `TimeZone`

Collator |  | DateFormatSymbols