org.joda.time.ReadablePeriod Maven / Gradle / Ivy
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/*
* Copyright 2001-2005 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 a time period specified in terms of individual duration fields
* such as years and days.
*
* The implementation of this interface may be mutable or immutable. This
* interface only gives access to retrieve data, never to change it.
*
* Periods are split up into multiple fields, for example days and seconds.
* Implementations are not required to evenly distribute the values across the fields.
* The value for each field may be positive or negative.
*
* When a time period is added to an instant, the effect is to add each field in turn.
* For example, a time period could be defined as 3 months, 2 days and -1 hours.
* In most circumstances this would be the same as 3 months, 1 day, and 23 hours.
* However, when adding across a daylight savings boundary, a day may be 23 or 25 hours long.
* Thus, the time period is always added field by field to the datetime.
*
* Periods are independent of chronology, and can only be treated as durations
* when paired with a time via an interval.
*
* @see ReadableDuration
* @see ReadableInterval
* @author Brian S O'Neill
* @author Stephen Colebourne
* @since 1.0
*/
public interface ReadablePeriod {
/**
* Gets the period type that defines which fields are included in the period.
*
* @return the period type
*/
PeriodType getPeriodType();
/**
* Gets the number of fields that this period supports.
*
* @return the number of fields supported
*/
int size();
/**
* Gets the field type at the specified index.
*
* @param index the index to retrieve
* @return the field at the specified index
* @throws IndexOutOfBoundsException if the index is invalid
*/
DurationFieldType getFieldType(int index);
/**
* Gets the value at the specified index.
*
* @param index the index to retrieve
* @return the value of the field at the specified index
* @throws IndexOutOfBoundsException if the index is invalid
*/
int getValue(int index);
/**
* Gets the value of one of the fields.
*
* If the field type specified is not supported by the period then zero
* is returned.
*
* @param field the field type to query, null returns zero
* @return the value of that field, zero if field not supported
*/
int get(DurationFieldType field);
/**
* Checks whether the field type specified is supported by this period.
*
* @param field the field to check, may be null which returns false
* @return true if the field is supported
*/
boolean isSupported(DurationFieldType field);
//-----------------------------------------------------------------------
/**
* Get this period as an immutable Period object.
*
* This will either typecast this instance, or create a new Period.
*
* @return a Duration using the same field set and values
*/
Period toPeriod();
/**
* Get this object as a MutablePeriod.
*
* This will always return a new MutablePeriod with the same fields.
*
* @return a MutablePeriod using the same field set and values
*/
MutablePeriod toMutablePeriod();
//-----------------------------------------------------------------------
/**
* Compares this object with the specified object for equality based
* on the value and type of each supported field.
* All ReadablePeriod instances are accepted.
*
* Note that a period of 1 day is not equal to a period of 24 hours,
* nor is 1 hour equal to 60 minutes. Only periods with the same amount
* in each field are equal.
*
* This is because periods represent an abstracted definition of a time
* period (eg. a day may not actually be 24 hours, it might be 23 or 25
* at daylight savings boundary).
*
* To compare the actual duration of two periods, convert both to
* {@link Duration}s, an operation that emphasises that the result may
* differ according to the date you choose.
*
* @param readablePeriod a readable period to check against
* @return true if all the field values and types are equal, false if
* not or the period is null or of an incorrect type
*/
boolean equals(Object readablePeriod);
/**
* Gets a hash code for the period that is compatible with the equals method.
* The hashcode is calculated as follows:
*
* int total = 17;
* for (int i = 0; i < fields.length; i++) {
* total = 27 * total + getValue(i);
* total = 27 * total + getFieldType(i).hashCode();
* }
* return total;
*
*
* @return a hash code
*/
int hashCode();
//-----------------------------------------------------------------------
/**
* Gets the value as a String in the style of the ISO8601 duration format.
* Technically, the output can breach the ISO specification as weeks may be included.
*
* For example, "PT6H3M5S" represents 6 hours, 3 minutes, 5 seconds.
*
* @return the value as an ISO8601 style string
*/
String toString();
}