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/*
* Copyright 2001-2009 Stephen Colebourne
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.joda.time;
/**
* Defines an instant in the datetime continuum.
* This interface expresses the datetime as milliseconds from 1970-01-01T00:00:00Z.
*
* The implementation of this interface may be mutable or immutable.
* This interface only gives access to retrieve data, never to change it.
*
* Methods in your application should be defined using ReadableInstant
* as a parameter if the method only wants to read the instant without needing to know
* the specific datetime fields.
*
* The {@code compareTo} method is no longer defined in this class in version 2.0.
* Instead, the definition is simply inherited from the {@code Comparable} interface.
* This approach is necessary to preserve binary compatibility.
* The definition of the comparison is ascending order by millisecond instant.
* Implementors are recommended to extend {@code AbstractInstant} instead of this interface.
*
* @author Stephen Colebourne
* @since 1.0
*/
public interface ReadableInstant extends Comparable {
/**
* Get the value as the number of milliseconds since
* the epoch, 1970-01-01T00:00:00Z.
*
* @return the value as milliseconds
*/
long getMillis();
/**
* Gets the chronology of the instant.
*
* The {@link Chronology} provides conversion from the millisecond
* value to meaningful fields in a particular calendar system.
*
* @return the Chronology, never null
*/
Chronology getChronology();
/**
* Gets the time zone of the instant from the chronology.
*
* @return the DateTimeZone that the instant is using, never null
*/
DateTimeZone getZone();
/**
* Get the value of one of the fields of a datetime.
*
* This method uses the chronology of the instant to obtain the value.
*
* @param type a field type, usually obtained from DateTimeFieldType, not null
* @return the value of that field
* @throws IllegalArgumentException if the field type is null
*/
int get(DateTimeFieldType type);
/**
* Checks whether the field type specified is supported by this implementation.
*
* @param field the field type to check, may be null which returns false
* @return true if the field is supported
*/
boolean isSupported(DateTimeFieldType field);
//-----------------------------------------------------------------------
/**
* Get the value as a simple immutable Instant object.
*
* This can be useful if you don't trust the implementation
* of the interface to be well-behaved, or to get a guaranteed
* immutable object.
*
* @return the value as an Instant object
*/
Instant toInstant();
//-----------------------------------------------------------------------
// Method is no longer defined here as that would break generic backwards compatibility
// /**
// * Compares this object with the specified object for ascending
// * millisecond instant order. This ordering is inconsistent with
// * equals, as it ignores the Chronology.
// *
// * All ReadableInstant instances are accepted.
// *
// * @param readableInstant a readable instant to check against
// * @return negative value if this is less, 0 if equal, or positive value if greater
// * @throws NullPointerException if the object is null
// * @throws ClassCastException if the object type is not supported
// */
// int compareTo(ReadableInstant readableInstant);
//-----------------------------------------------------------------------
/**
* Is this instant equal to the instant passed in
* comparing solely by millisecond.
*
* @param instant an instant to check against, null means now
* @return true if the instant is equal to the instant passed in
*/
boolean isEqual(ReadableInstant instant);
/**
* Is this instant after the instant passed in
* comparing solely by millisecond.
*
* @param instant an instant to check against, null means now
* @return true if the instant is after the instant passed in
*/
boolean isAfter(ReadableInstant instant);
/**
* Is this instant before the instant passed in
* comparing solely by millisecond.
*
* @param instant an instant to check against, null means now
* @return true if the instant is before the instant passed in
*/
boolean isBefore(ReadableInstant instant);
//-----------------------------------------------------------------------
/**
* Compares this object with the specified object for equality based
* on the millisecond instant and the Chronology. All ReadableInstant
* instances are accepted.
*
* To compare two instants for absolute time (ie. UTC milliseconds
* ignoring the chronology), use {@link #isEqual(ReadableInstant)} or
* {@link #compareTo(Object)}.
*
* @param readableInstant a readable instant to check against
* @return true if millisecond and chronology are equal, false if
* not or the instant is null or of an incorrect type
*/
boolean equals(Object readableInstant);
/**
* Gets a hash code for the instant that is compatible with the
* equals method.
*
* The formula used must be as follows:
*
* ((int) (getMillis() ^ (getMillis() >>> 32))) +
* (getChronology().hashCode())
*
*
* @return a hash code as defined above
*/
int hashCode();
//-----------------------------------------------------------------------
/**
* Get the value as a String in a recognisable ISO8601 format.
*
* The string output is in ISO8601 format to enable the String
* constructor to correctly parse it.
*
* @return the value as an ISO8601 string
*/
String toString();
}