org.joda.time
Class DurationField

java.lang.Object
  org.joda.time.DurationField

All Implemented Interfaces:

Comparable<DurationField>

Direct Known Subclasses:

BaseDurationField, DelegatedDurationField, MillisDurationField, UnsupportedDurationField

public abstract class DurationField
extends Object
implements Comparable<DurationField>

Defines the calculation engine for duration fields. The interface defines a set of methods that manipulate a millisecond duration with regards to a single field, such as months or seconds.

This design is extensible so, if you wish, you can extract a different field from the millisecond duration. A number of standard implementations are provided to assist.

Since:

1.0

DurationField

public DurationField()

getType

public abstract DurationFieldType getType()

Get the type of the field.

Returns:

field type

getName

public abstract String getName()

Get the name of the field.

By convention, names are plural.

Returns:

field name

isSupported

public abstract boolean isSupported()

Returns true if this field is supported.

Returns:

true if this field is supported

isPrecise

public abstract boolean isPrecise()

Is this field precise. A precise field can calculate its value from milliseconds without needing a reference date. Put another way, a precise field's unit size is not variable.

Returns:

true if precise

See Also:

getUnitMillis()

getUnitMillis

public abstract long getUnitMillis()

Returns the amount of milliseconds per unit value of this field. For example, if this field represents "seconds", then this returns the milliseconds in one second.

For imprecise fields, the unit size is variable, and so this method returns a suitable average value.

Returns:

the unit size of this field, in milliseconds

See Also:

isPrecise()

getValue

public abstract int getValue(long duration)

Get the value of this field from the milliseconds, which is approximate if this field is imprecise.

Parameters:

duration - the milliseconds to query, which may be negative

Returns:

the value of the field, in the units of the field, which may be negative

Throws:

ArithmeticException - if the value is too large for an int

getValueAsLong

public abstract long getValueAsLong(long duration)

Get the value of this field from the milliseconds, which is approximate if this field is imprecise.

Parameters:

duration - the milliseconds to query, which may be negative

Returns:

the value of the field, in the units of the field, which may be negative

getValue

public abstract int getValue(long duration,
                             long instant)

Get the value of this field from the milliseconds relative to an instant. For precise fields this method produces the same result as for the single argument get method.

If the millisecond duration is positive, then the instant is treated as a "start instant". If negative, the instant is treated as an "end instant".

Parameters:

duration - the milliseconds to query, which may be negative

instant - the start instant to calculate relative to

Returns:

the value of the field, in the units of the field, which may be negative

Throws:

ArithmeticException - if the value is too large for an int

getValueAsLong

public abstract long getValueAsLong(long duration,
                                    long instant)

Get the value of this field from the milliseconds relative to an instant. For precise fields this method produces the same result as for the single argument get method.

If the millisecond duration is positive, then the instant is treated as a "start instant". If negative, the instant is treated as an "end instant".

Parameters:

duration - the milliseconds to query, which may be negative

instant - the start instant to calculate relative to

Returns:

the value of the field, in the units of the field, which may be negative

getMillis

public abstract long getMillis(int value)

Get the millisecond duration of this field from its value, which is approximate if this field is imprecise.

Parameters:

value - the value of the field, which may be negative

Returns:

the milliseconds that the field represents, which may be negative

getMillis

public abstract long getMillis(long value)

Get the millisecond duration of this field from its value, which is approximate if this field is imprecise.

Parameters:

value - the value of the field, which may be negative

Returns:

the milliseconds that the field represents, which may be negative

getMillis

public abstract long getMillis(int value,
                               long instant)

Get the millisecond duration of this field from its value relative to an instant. For precise fields this method produces the same result as for the single argument getMillis method.

If the value is positive, then the instant is treated as a "start instant". If negative, the instant is treated as an "end instant".

Parameters:

value - the value of the field, which may be negative

instant - the instant to calculate relative to

Returns:

the millisecond duration that the field represents, which may be negative

getMillis

public abstract long getMillis(long value,
                               long instant)

Get the millisecond duration of this field from its value relative to an instant. For precise fields this method produces the same result as for the single argument getMillis method.

If the value is positive, then the instant is treated as a "start instant". If negative, the instant is treated as an "end instant".

Parameters:

value - the value of the field, which may be negative

instant - the instant to calculate relative to

Returns:

the millisecond duration that the field represents, which may be negative

add

public abstract long add(long instant,
                         int value)

Adds a duration value (which may be negative) to the instant.

Parameters:

instant - the milliseconds from 1970-01-01T00:00:00Z to add to

value - the value to add, in the units of the field

Returns:

the updated milliseconds

add

public abstract long add(long instant,
                         long value)

Adds a duration value (which may be negative) to the instant.

Parameters:

instant - the milliseconds from 1970-01-01T00:00:00Z to add to

value - the value to add, in the units of the field

Returns:

the updated milliseconds

subtract

public long subtract(long instant,
                     int value)

Subtracts a duration value (which may be negative) from the instant.

Parameters:

instant - the milliseconds from 1970-01-01T00:00:00Z to subtract from

value - the value to subtract, in the units of the field

Returns:

the updated milliseconds

Since:

1.1

subtract

public long subtract(long instant,
                     long value)

Subtracts a duration value (which may be negative) from the instant.

Parameters:

instant - the milliseconds from 1970-01-01T00:00:00Z to subtract from

value - the value to subtract, in the units of the field

Returns:

the updated milliseconds

Since:

1.1

getDifference

public abstract int getDifference(long minuendInstant,
                                  long subtrahendInstant)

Computes the difference between two instants, as measured in the units of this field. Any fractional units are dropped from the result. Calling getDifference reverses the effect of calling add. In the following code:

 long instant = ...
 int v = ...
 int age = getDifference(add(instant, v), instant);
 

The value 'age' is the same as the value 'v'.

Parameters:

minuendInstant - the milliseconds from 1970-01-01T00:00:00Z to subtract from

subtrahendInstant - the milliseconds from 1970-01-01T00:00:00Z to subtract off the minuend

Returns:

the difference in the units of this field

getDifferenceAsLong

public abstract long getDifferenceAsLong(long minuendInstant,
                                         long subtrahendInstant)

Computes the difference between two instants, as measured in the units of this field. Any fractional units are dropped from the result. Calling getDifference reverses the effect of calling add. In the following code:

 long instant = ...
 long v = ...
 long age = getDifferenceAsLong(add(instant, v), instant);
 

The value 'age' is the same as the value 'v'.

Parameters:

minuendInstant - the milliseconds from 1970-01-01T00:00:00Z to subtract from

subtrahendInstant - the milliseconds from 1970-01-01T00:00:00Z to subtract off the minuend

Returns:

the difference in the units of this field

toString

public abstract String toString()

Get a suitable debug string.

Overrides:

toString in class Object

Returns:

debug string