Java tutorial
/* * Copyright 2001-2013 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 years. * <p> * <code>Years</code> is an immutable period that can only store years. * It does not store months, days or hours for example. As such it is a * type-safe way of representing a number of years in an application. * <p> * The number of years is set in the constructor, and may be queried using * <code>getYears()</code>. Basic mathematical operations are provided - * <code>plus()</code>, <code>minus()</code>, <code>multipliedBy()</code> and * <code>dividedBy()</code>. * <p> * <code>Years</code> is thread-safe and immutable. * * @author Stephen Colebourne * @since 1.4 */ public final class Years extends BaseSingleFieldPeriod { /** Constant representing zero years. */ public static final Years ZERO = new Years(0); /** Constant representing one year. */ public static final Years ONE = new Years(1); /** Constant representing two years. */ public static final Years TWO = new Years(2); /** Constant representing three years. */ public static final Years THREE = new Years(3); /** Constant representing the maximum number of years that can be stored in this object. */ public static final Years MAX_VALUE = new Years(Integer.MAX_VALUE); /** Constant representing the minimum number of years that can be stored in this object. */ public static final Years MIN_VALUE = new Years(Integer.MIN_VALUE); /** The parser to use for this class. */ private static final PeriodFormatter PARSER = ISOPeriodFormat.standard().withParseType(PeriodType.years()); /** Serialization version. */ private static final long serialVersionUID = 87525275727380868L; //----------------------------------------------------------------------- /** * Obtains an instance of <code>Years</code> that may be cached. * <code>Years</code> is immutable, so instances can be cached and shared. * This factory method provides access to shared instances. * * @param years the number of years to obtain an instance for * @return the instance of Years */ public static Years years(int years) { switch (years) { case 0: return ZERO; case 1: return ONE; case 2: return TWO; case 3: return THREE; case Integer.MAX_VALUE: return MAX_VALUE; case Integer.MIN_VALUE: return MIN_VALUE; default: return new Years(years); } } //----------------------------------------------------------------------- /** * Creates a <code>Years</code> representing the number of whole years * between the two specified datetimes. This method correctly handles * any daylight savings time changes that may occur during the interval. * * @param start the start instant, must not be null * @param end the end instant, must not be null * @return the period in years * @throws IllegalArgumentException if the instants are null or invalid */ public static Years yearsBetween(ReadableInstant start, ReadableInstant end) { int amount = BaseSingleFieldPeriod.between(start, end, DurationFieldType.years()); return Years.years(amount); } /** * Creates a <code>Years</code> representing the number of whole years * 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. * * @param start the start partial date, must not be null * @param end the end partial date, must not be null * @return the period in years * @throws IllegalArgumentException if the partials are null or invalid */ public static Years yearsBetween(ReadablePartial start, ReadablePartial end) { if (start instanceof LocalDate && end instanceof LocalDate) { Chronology chrono = DateTimeUtils.getChronology(start.getChronology()); int years = chrono.years().getDifference(((LocalDate) end).getLocalMillis(), ((LocalDate) start).getLocalMillis()); return Years.years(years); } int amount = BaseSingleFieldPeriod.between(start, end, ZERO); return Years.years(amount); } /** * Creates a <code>Years</code> representing the number of whole years * 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 years from, null returns zero * @return the period in years * @throws IllegalArgumentException if the partials are null or invalid */ public static Years yearsIn(ReadableInterval interval) { if (interval == null) { return Years.ZERO; } int amount = BaseSingleFieldPeriod.between(interval.getStart(), interval.getEnd(), DurationFieldType.years()); return Years.years(amount); } /** * Creates a new <code>Years</code> by parsing a string in the ISO8601 format 'PnY'. * <p> * The parse will accept the full ISO syntax of PnYnMnWnDTnHnMnS however only the * years 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 years * @throws IllegalArgumentException if the string format is invalid */ @FromString public static Years parseYears(String periodStr) { if (periodStr == null) { return Years.ZERO; } Period p = PARSER.parsePeriod(periodStr); return Years.years(p.getYears()); } //----------------------------------------------------------------------- /** * Creates a new instance representing a number of years. * You should consider using the factory method {@link #years(int)} * instead of the constructor. * * @param years the number of years to represent */ private Years(int years) { super(years); } /** * Resolves singletons. * * @return the singleton instance */ private Object readResolve() { return Years.years(getValue()); } //----------------------------------------------------------------------- /** * Gets the duration field type, which is <code>years</code>. * * @return the period type */ public DurationFieldType getFieldType() { return DurationFieldType.years(); } /** * Gets the period type, which is <code>years</code>. * * @return the period type */ public PeriodType getPeriodType() { return PeriodType.years(); } //----------------------------------------------------------------------- /** * Gets the number of years that this period represents. * * @return the number of years in the period */ public int getYears() { return getValue(); } //----------------------------------------------------------------------- /** * Returns a new instance with the specified number of years added. * <p> * This instance is immutable and unaffected by this method call. * * @param years the amount of years to add, may be negative * @return the new period plus the specified number of years * @throws ArithmeticException if the result overflows an int */ public Years plus(int years) { if (years == 0) { return this; } return Years.years(FieldUtils.safeAdd(getValue(), years)); } /** * Returns a new instance with the specified number of years added. * <p> * This instance is immutable and unaffected by this method call. * * @param years the amount of years to add, may be negative, null means zero * @return the new period plus the specified number of years * @throws ArithmeticException if the result overflows an int */ public Years plus(Years years) { if (years == null) { return this; } return plus(years.getValue()); } //----------------------------------------------------------------------- /** * Returns a new instance with the specified number of years taken away. * <p> * This instance is immutable and unaffected by this method call. * * @param years the amount of years to take away, may be negative * @return the new period minus the specified number of years * @throws ArithmeticException if the result overflows an int */ public Years minus(int years) { return plus(FieldUtils.safeNegate(years)); } /** * Returns a new instance with the specified number of years taken away. * <p> * This instance is immutable and unaffected by this method call. * * @param years the amount of years to take away, may be negative, null means zero * @return the new period minus the specified number of years * @throws ArithmeticException if the result overflows an int */ public Years minus(Years years) { if (years == null) { return this; } return minus(years.getValue()); } //----------------------------------------------------------------------- /** * Returns a new instance with the years 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 Years multipliedBy(int scalar) { return Years.years(FieldUtils.safeMultiply(getValue(), scalar)); } /** * Returns a new instance with the years 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 Years dividedBy(int divisor) { if (divisor == 1) { return this; } return Years.years(getValue() / divisor); } //----------------------------------------------------------------------- /** * Returns a new instance with the years value negated. * * @return the new period with a negated value * @throws ArithmeticException if the result overflows an int */ public Years negated() { return Years.years(FieldUtils.safeNegate(getValue())); } //----------------------------------------------------------------------- /** * Is this years instance greater than the specified number of years. * * @param other the other period, null means zero * @return true if this years instance is greater than the specified one */ public boolean isGreaterThan(Years other) { if (other == null) { return getValue() > 0; } return getValue() > other.getValue(); } /** * Is this years instance less than the specified number of years. * * @param other the other period, null means zero * @return true if this years instance is less than the specified one */ public boolean isLessThan(Years 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, "P4Y" represents 4 years. * * @return the value as an ISO8601 string */ @ToString public String toString() { return "P" + String.valueOf(getValue()) + "Y"; } }