/*
* Copyright 2001-2010 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;
import org.joda.convert.
FromString;
import org.joda.convert.
ToString;
import org.joda.time.base.
BaseSingleFieldPeriod;
import org.joda.time.field.
FieldUtils;
import org.joda.time.format.
ISOPeriodFormat;
import org.joda.time.format.
PeriodFormatter;
/**
* An immutable time period representing a number of months.
* <p>
* <code>Months</code> is an immutable period that can only store months.
* It does not store years, days or hours for example. As such it is a
* type-safe way of representing a number of months in an application.
* <p>
* The number of months is set in the constructor, and may be queried using
* <code>getMonths()</code>. Basic mathematical operations are provided -
* <code>plus()</code>, <code>minus()</code>, <code>multipliedBy()</code> and
* <code>dividedBy()</code>.
* <p>
* <code>Months</code> is thread-safe and immutable.
*
* @author Stephen Colebourne
* @since 1.4
*/
public final class
Months extends
BaseSingleFieldPeriod {
/** Constant representing zero months. */
public static final
Months ZERO = new
Months(0);
/** Constant representing one month. */
public static final
Months ONE = new
Months(1);
/** Constant representing two months. */
public static final
Months TWO = new
Months(2);
/** Constant representing three months. */
public static final
Months THREE = new
Months(3);
/** Constant representing four months. */
public static final
Months FOUR = new
Months(4);
/** Constant representing five months. */
public static final
Months FIVE = new
Months(5);
/** Constant representing six months. */
public static final
Months SIX = new
Months(6);
/** Constant representing seven months. */
public static final
Months SEVEN = new
Months(7);
/** Constant representing eight months. */
public static final
Months EIGHT = new
Months(8);
/** Constant representing nine months. */
public static final
Months NINE = new
Months(9);
/** Constant representing ten months. */
public static final
Months TEN = new
Months(10);
/** Constant representing eleven months. */
public static final
Months ELEVEN = new
Months(11);
/** Constant representing twelve months. */
public static final
Months TWELVE = new
Months(12);
/** Constant representing the maximum number of months that can be stored in this object. */
public static final
Months MAX_VALUE = new
Months(
Integer.
MAX_VALUE);
/** Constant representing the minimum number of months that can be stored in this object. */
public static final
Months MIN_VALUE = new
Months(
Integer.
MIN_VALUE);
/** The parser to use for this class. */
private static final
PeriodFormatter PARSER =
ISOPeriodFormat.
standard().
withParseType(
PeriodType.
months());
/** Serialization version. */
private static final long
serialVersionUID = 87525275727380867L;
//-----------------------------------------------------------------------
/**
* Obtains an instance of <code>Months</code> that may be cached.
* <code>Months</code> is immutable, so instances can be cached and shared.
* This factory method provides access to shared instances.
*
* @param months the number of months to obtain an instance for
* @return the instance of Months
*/
public static
Months months(int
months) {
switch (
months) {
case 0:
return
ZERO;
case 1:
return
ONE;
case 2:
return
TWO;
case 3:
return
THREE;
case 4:
return
FOUR;
case 5:
return
FIVE;
case 6:
return
SIX;
case 7:
return
SEVEN;
case 8:
return
EIGHT;
case 9:
return
NINE;
case 10:
return
TEN;
case 11:
return
ELEVEN;
case 12:
return
TWELVE;
case
Integer.
MAX_VALUE:
return
MAX_VALUE;
case
Integer.
MIN_VALUE:
return
MIN_VALUE;
default:
return new
Months(
months);
}
}
//-----------------------------------------------------------------------
/**
* Creates a <code>Months</code> representing the number of whole months
* between the two specified datetimes. This method correctly handles
* any daylight savings time changes that may occur during the interval.
* <p>
* This method calculates by adding months to the start date until the result
* is past the end date. As such, a period from the end of a "long" month to
* the end of a "short" month is counted as a whole month.
*
* @param start the start instant, must not be null
* @param end the end instant, must not be null
* @return the period in months
* @throws IllegalArgumentException if the instants are null or invalid
*/
public static
Months monthsBetween(
ReadableInstant start,
ReadableInstant end) {
int
amount =
BaseSingleFieldPeriod.
between(
start,
end,
DurationFieldType.
months());
return
Months.
months(
amount);
}
/**
* Creates a <code>Months</code> representing the number of whole months
* between the two specified partial datetimes.
* <p>
* The two partials must contain the same fields, for example you can specify
* two <code>LocalDate</code> objects.
* <p>
* This method calculates by adding months to the start date until the result
* is past the end date. As such, a period from the end of a "long" month to
* the end of a "short" month is counted as a whole month.
*
* @param start the start partial date, must not be null
* @param end the end partial date, must not be null
* @return the period in months
* @throws IllegalArgumentException if the partials are null or invalid
*/
public static
Months monthsBetween(
ReadablePartial start,
ReadablePartial end) {
if (
start instanceof
LocalDate &&
end instanceof
LocalDate) {
Chronology chrono =
DateTimeUtils.
getChronology(
start.
getChronology());
int
months =
chrono.
months().
getDifference(
((
LocalDate)
end).
getLocalMillis(), ((
LocalDate)
start).
getLocalMillis());
return
Months.
months(
months);
}
int
amount =
BaseSingleFieldPeriod.
between(
start,
end,
ZERO);
return
Months.
months(
amount);
}
/**
* Creates a <code>Months</code> representing the number of whole months
* in the specified interval. This method correctly handles any daylight
* savings time changes that may occur during the interval.
*
* @param interval the interval to extract months from, null returns zero
* @return the period in months
* @throws IllegalArgumentException if the partials are null or invalid
*/
public static
Months monthsIn(
ReadableInterval interval) {
if (
interval == null) {
return
Months.
ZERO;
}
int
amount =
BaseSingleFieldPeriod.
between(
interval.
getStart(),
interval.
getEnd(),
DurationFieldType.
months());
return
Months.
months(
amount);
}
/**
* Creates a new <code>Months</code> by parsing a string in the ISO8601 format 'PnM'.
* <p>
* The parse will accept the full ISO syntax of PnYnMnWnDTnHnMnS however only the
* months component may be non-zero. If any other component is non-zero, an exception
* will be thrown.
*
* @param periodStr the period string, null returns zero
* @return the period in months
* @throws IllegalArgumentException if the string format is invalid
*/
@
FromString
public static
Months parseMonths(
String periodStr) {
if (
periodStr == null) {
return
Months.
ZERO;
}
Period p =
PARSER.
parsePeriod(
periodStr);
return
Months.
months(
p.
getMonths());
}
//-----------------------------------------------------------------------
/**
* Creates a new instance representing a number of months.
* You should consider using the factory method {@link #months(int)}
* instead of the constructor.
*
* @param months the number of months to represent
*/
private
Months(int
months) {
super(
months);
}
/**
* Resolves singletons.
*
* @return the singleton instance
*/
private
Object readResolve() {
return
Months.
months(
getValue());
}
//-----------------------------------------------------------------------
/**
* Gets the duration field type, which is <code>months</code>.
*
* @return the period type
*/
public
DurationFieldType getFieldType() {
return
DurationFieldType.
months();
}
/**
* Gets the period type, which is <code>months</code>.
*
* @return the period type
*/
public
PeriodType getPeriodType() {
return
PeriodType.
months();
}
//-----------------------------------------------------------------------
/**
* Gets the number of months that this period represents.
*
* @return the number of months in the period
*/
public int
getMonths() {
return
getValue();
}
//-----------------------------------------------------------------------
/**
* Returns a new instance with the specified number of months added.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param months the amount of months to add, may be negative
* @return the new period plus the specified number of months
* @throws ArithmeticException if the result overflows an int
*/
public
Months plus(int
months) {
if (
months == 0) {
return this;
}
return
Months.
months(
FieldUtils.
safeAdd(
getValue(),
months));
}
/**
* Returns a new instance with the specified number of months added.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param months the amount of months to add, may be negative, null means zero
* @return the new period plus the specified number of months
* @throws ArithmeticException if the result overflows an int
*/
public
Months plus(
Months months) {
if (
months == null) {
return this;
}
return
plus(
months.
getValue());
}
//-----------------------------------------------------------------------
/**
* Returns a new instance with the specified number of months taken away.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param months the amount of months to take away, may be negative
* @return the new period minus the specified number of months
* @throws ArithmeticException if the result overflows an int
*/
public
Months minus(int
months) {
return
plus(
FieldUtils.
safeNegate(
months));
}
/**
* Returns a new instance with the specified number of months taken away.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param months the amount of months to take away, may be negative, null means zero
* @return the new period minus the specified number of months
* @throws ArithmeticException if the result overflows an int
*/
public
Months minus(
Months months) {
if (
months == null) {
return this;
}
return
minus(
months.
getValue());
}
//-----------------------------------------------------------------------
/**
* Returns a new instance with the months multiplied by the specified scalar.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param scalar the amount to multiply by, may be negative
* @return the new period multiplied by the specified scalar
* @throws ArithmeticException if the result overflows an int
*/
public
Months multipliedBy(int
scalar) {
return
Months.
months(
FieldUtils.
safeMultiply(
getValue(),
scalar));
}
/**
* Returns a new instance with the months divided by the specified divisor.
* The calculation uses integer division, thus 3 divided by 2 is 1.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param divisor the amount to divide by, may be negative
* @return the new period divided by the specified divisor
* @throws ArithmeticException if the divisor is zero
*/
public
Months dividedBy(int
divisor) {
if (
divisor == 1) {
return this;
}
return
Months.
months(
getValue() /
divisor);
}
//-----------------------------------------------------------------------
/**
* Returns a new instance with the months value negated.
*
* @return the new period with a negated value
* @throws ArithmeticException if the result overflows an int
*/
public
Months negated() {
return
Months.
months(
FieldUtils.
safeNegate(
getValue()));
}
//-----------------------------------------------------------------------
/**
* Is this months instance greater than the specified number of months.
*
* @param other the other period, null means zero
* @return true if this months instance is greater than the specified one
*/
public boolean
isGreaterThan(
Months other) {
if (
other == null) {
return
getValue() > 0;
}
return
getValue() >
other.
getValue();
}
/**
* Is this months instance less than the specified number of months.
*
* @param other the other period, null means zero
* @return true if this months instance is less than the specified one
*/
public boolean
isLessThan(
Months other) {
if (
other == null) {
return
getValue() < 0;
}
return
getValue() <
other.
getValue();
}
//-----------------------------------------------------------------------
/**
* Gets this instance as a String in the ISO8601 duration format.
* <p>
* For example, "P4M" represents 4 months.
*
* @return the value as an ISO8601 string
*/
@
ToString
public
String toString() {
return "P" +
String.
valueOf(
getValue()) + "M";
}
}