[Chapter 30] 30.2 java.util.Calendar (JDK 1.1)

#

| Chapter 30 The java.util Package |

## 30.2 java.util.Calendar (JDK 1.1)

###

This abstract class defines methods used to perform date and time arithmetic. It also includes methods that convert dates and times to and from the machine-usable millisecond format used by the `Date` class and units like minutes, hours, days, weeks, months, and years that are more useful to humans.

As an abstract class, `Calendar` cannot be directly instantiated. Instead, it provides static `getInstance()` methods that return instances of a `Calendar` subclass suitable for use in a specified or default locale with a specified or default time zone.

`Calendar` defines a number of useful constants. Some of these are values that represent days of the week and months of the year. Other constants, such as `HOUR` and `DAY_OF_WEEK`, represent various fields of date and time information. These field constants are passed to a number of `Calendar` methods, such as `get()` and `set()`, in order to indicate what particular date or time field is of interest.

`setTime()` and the various `set()` methods set the date represented by a `Calendar` object. The `add()` method adds (or subtracts) values to a calendar field, incrementing the next larger field when the field "rolls over." `roll()` does the same, without modifying any but the specified field. `before()` and `after()` compare two `Calendar` objects.

Many of the methods of the `Calendar` class are replacements for methods of Date that have been deprecated in Java 1.1. While the `Calendar` class is used to convert a time value into its various hour, day, month, and other fields, it is not intended to present those fields into a form suitable for display to the end user. That function is performed by the `DateFormat` class in the `java.text` package, which handles internationalization issues.

See also `Date`, `DateFormat`, and `TimeZone`.

    public abstract class Calendar extends Object implements Serializable, Cloneable {
        // Protected Constructors
                protected Calendar();
                protected Calendar(TimeZone zone, Locale aLocale);
        // Constants
                public static final int FIELD_COUNT;
        // Date and Time Field Constants
                public static final int ERA;
                public static final int YEAR;
                public static final int MONTH;
                public static final int WEEK_OF_YEAR, WEEK_OF_MONTH;
                public static final int DATE, DAY_OF_MONTH;
                public static final int DAY_OF_YEAR, DAY_OF_WEEK, DAY_OF_WEEK_IN_MONTH;
                public static final int ZONE_OFFSET, DST_OFFSET;
                public static final int AM_PM;
                public static final int HOUR, HOUR_OF_DAY;
                public static final int MINUTE;
                public static final int SECOND;
                public static final int MILLISECOND;
        // Field Value Constants
                public static final int JANUARY, FEBRUARY, MARCH, APRIL;
                public static final int MAY, JUNE, JULY, AUGUST;
                public static final int SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER;
                public static final int UNDECIMBER;
                public static final int SUNDAY, MONDAY, TUESDAY, WEDNESDAY;
                public static final int THURSDAY, FRIDAY, SATURDAY;
                public static final int AM, PM;
        // Protected Instance Variables
                protected boolean areFieldsSet;
                protected int[] fields;
                protected boolean[] isSet;
                protected boolean isTimeSet;
                protected long time;
        // Class Methods
                public static synchronized Locale[] getAvailableLocales();
                public static synchronized Calendar getInstance();
                public static synchronized Calendar getInstance(TimeZone zone);
                public static synchronized Calendar getInstance(Locale aLocale);
                public static synchronized Calendar getInstance(TimeZone zone, Locale aLocale);
        // Public Instance Methods
                public abstract void add(int field, int amount);
                public abstract boolean after(Object when);
                public abstract boolean before(Object when);
                public final void clear();
                public final void clear(int field);
                public Object clone();  // Overrides Object
                public abstract boolean equals(Object when);  // Overrides Object
                public final int get(int field);
                public int getFirstDayOfWeek();
                public abstract int getGreatestMinimum(int field);
                public abstract int getLeastMaximum(int field);
                public abstract int getMaximum(int field);
                public int getMinimalDaysInFirstWeek();
                public abstract int getMinimum(int field);
                public final Date getTime();
                public TimeZone getTimeZone();
                public boolean isLenient();
                public final boolean isSet(int field);
                public abstract void roll(int field, boolean up);
                public final void set(int field, int value);
                public final void set(int year, int month, int date);
                public final void set(int year, int month, int date, int hour, int minute);
                public final void set(int year, int month, int date, int hour, int minute, int second);
                public void setFirstDayOfWeek(int value);
                public void setLenient(boolean lenient);
                public void setMinimalDaysInFirstWeek(int value);
                public final void setTime(Date date);
                public void setTimeZone(TimeZone value);
        // Protected Instance Methods
                protected void complete();
                protected abstract void computeFields();
                protected abstract void computeTime();
                protected long getTimeInMillis();
                protected final int internalGet(int field);
                protected void setTimeInMillis(long millis);
    }

### Extended By:

GregorianCalendar

### Passed To:

DateFormat.setCalendar()

### Returned By:

Calendar.getInstance(), DateFormat.getCalendar()

### Type Of:

DateFormat.calendar

java.util.BitSet (JDK 1.0) |  | java.util.Date (JDK 1.0)