001 /* 002 * Copyright 2001-2006 Stephen Colebourne 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 package org.joda.time; 017 018 import org.joda.time.base.BaseSingleFieldPeriod; 019 import org.joda.time.field.FieldUtils; 020 import org.joda.time.format.ISOPeriodFormat; 021 import org.joda.time.format.PeriodFormatter; 022 023 /** 024 * An immutable time period representing a number of months. 025 * <p> 026 * <code>Months</code> is an immutable period that can only store months. 027 * It does not store years, days or hours for example. As such it is a 028 * type-safe way of representing a number of months in an application. 029 * <p> 030 * The number of months is set in the constructor, and may be queried using 031 * <code>getMonths()</code>. Basic mathematical operations are provided - 032 * <code>plus()</code>, <code>minus()</code>, <code>multipliedBy()</code> and 033 * <code>dividedBy()</code>. 034 * <p> 035 * <code>Months</code> is thread-safe and immutable. 036 * 037 * @author Stephen Colebourne 038 * @since 1.4 039 */ 040 public final class Months extends BaseSingleFieldPeriod { 041 042 /** Constant representing zero months. */ 043 public static final Months ZERO = new Months(0); 044 /** Constant representing one month. */ 045 public static final Months ONE = new Months(1); 046 /** Constant representing two months. */ 047 public static final Months TWO = new Months(2); 048 /** Constant representing three months. */ 049 public static final Months THREE = new Months(3); 050 /** Constant representing four months. */ 051 public static final Months FOUR = new Months(4); 052 /** Constant representing five months. */ 053 public static final Months FIVE = new Months(5); 054 /** Constant representing six months. */ 055 public static final Months SIX = new Months(6); 056 /** Constant representing seven months. */ 057 public static final Months SEVEN = new Months(7); 058 /** Constant representing eight months. */ 059 public static final Months EIGHT = new Months(8); 060 /** Constant representing nine months. */ 061 public static final Months NINE = new Months(9); 062 /** Constant representing ten months. */ 063 public static final Months TEN = new Months(10); 064 /** Constant representing eleven months. */ 065 public static final Months ELEVEN = new Months(11); 066 /** Constant representing twelve months. */ 067 public static final Months TWELVE = new Months(12); 068 /** Constant representing the maximum number of months that can be stored in this object. */ 069 public static final Months MAX_VALUE = new Months(Integer.MAX_VALUE); 070 /** Constant representing the minimum number of months that can be stored in this object. */ 071 public static final Months MIN_VALUE = new Months(Integer.MIN_VALUE); 072 073 /** The parser to use for this class. */ 074 private static final PeriodFormatter PARSER = ISOPeriodFormat.standard().withParseType(PeriodType.months()); 075 /** Serialization version. */ 076 private static final long serialVersionUID = 87525275727380867L; 077 078 //----------------------------------------------------------------------- 079 /** 080 * Obtains an instance of <code>Months</code> that may be cached. 081 * <code>Months</code> is immutable, so instances can be cached and shared. 082 * This factory method provides access to shared instances. 083 * 084 * @param months the number of months to obtain an instance for 085 * @return the instance of Months 086 */ 087 public static Months months(int months) { 088 switch (months) { 089 case 0: 090 return ZERO; 091 case 1: 092 return ONE; 093 case 2: 094 return TWO; 095 case 3: 096 return THREE; 097 case 4: 098 return FOUR; 099 case 5: 100 return FIVE; 101 case 6: 102 return SIX; 103 case 7: 104 return SEVEN; 105 case 8: 106 return EIGHT; 107 case 9: 108 return NINE; 109 case 10: 110 return TEN; 111 case 11: 112 return ELEVEN; 113 case 12: 114 return TWELVE; 115 case Integer.MAX_VALUE: 116 return MAX_VALUE; 117 case Integer.MIN_VALUE: 118 return MIN_VALUE; 119 default: 120 return new Months(months); 121 } 122 } 123 124 //----------------------------------------------------------------------- 125 /** 126 * Creates a <code>Months</code> representing the number of whole months 127 * between the two specified datetimes. This method corectly handles 128 * any daylight savings time changes that may occur during the interval. 129 * 130 * @param start the start instant, must not be null 131 * @param end the end instant, must not be null 132 * @return the period in months 133 * @throws IllegalArgumentException if the instants are null or invalid 134 */ 135 public static Months monthsBetween(ReadableInstant start, ReadableInstant end) { 136 int amount = BaseSingleFieldPeriod.between(start, end, DurationFieldType.months()); 137 return Months.months(amount); 138 } 139 140 /** 141 * Creates a <code>Months</code> representing the number of whole months 142 * between the two specified partial datetimes. 143 * <p> 144 * The two partials must contain the same fields, for example you can specify 145 * two <code>LocalDate</code> objects. 146 * 147 * @param start the start partial date, must not be null 148 * @param end the end partial date, must not be null 149 * @return the period in months 150 * @throws IllegalArgumentException if the partials are null or invalid 151 */ 152 public static Months monthsBetween(ReadablePartial start, ReadablePartial end) { 153 if (start instanceof LocalDate && end instanceof LocalDate) { 154 Chronology chrono = DateTimeUtils.getChronology(start.getChronology()); 155 int months = chrono.months().getDifference( 156 ((LocalDate) end).getLocalMillis(), ((LocalDate) start).getLocalMillis()); 157 return Months.months(months); 158 } 159 int amount = BaseSingleFieldPeriod.between(start, end, ZERO); 160 return Months.months(amount); 161 } 162 163 /** 164 * Creates a <code>Months</code> representing the number of whole months 165 * in the specified interval. This method corectly handles any daylight 166 * savings time changes that may occur during the interval. 167 * 168 * @param interval the interval to extract months from, null returns zero 169 * @return the period in months 170 * @throws IllegalArgumentException if the partials are null or invalid 171 */ 172 public static Months monthsIn(ReadableInterval interval) { 173 if (interval == null) { 174 return Months.ZERO; 175 } 176 int amount = BaseSingleFieldPeriod.between(interval.getStart(), interval.getEnd(), DurationFieldType.months()); 177 return Months.months(amount); 178 } 179 180 /** 181 * Creates a new <code>Months</code> by parsing a string in the ISO8601 format 'PnM'. 182 * <p> 183 * The parse will accept the full ISO syntax of PnYnMnWnDTnHnMnS however only the 184 * months component may be non-zero. If any other component is non-zero, an exception 185 * will be thrown. 186 * 187 * @param periodStr the period string, null returns zero 188 * @return the period in months 189 * @throws IllegalArgumentException if the string format is invalid 190 */ 191 public static Months parseMonths(String periodStr) { 192 if (periodStr == null) { 193 return Months.ZERO; 194 } 195 Period p = PARSER.parsePeriod(periodStr); 196 return Months.months(p.getMonths()); 197 } 198 199 //----------------------------------------------------------------------- 200 /** 201 * Creates a new instance representing a number of months. 202 * You should consider using the factory method {@link #months(int)} 203 * instead of the constructor. 204 * 205 * @param months the number of months to represent 206 */ 207 private Months(int months) { 208 super(months); 209 } 210 211 /** 212 * Resolves singletons. 213 * 214 * @return the singleton instance 215 */ 216 private Object readResolve() { 217 return Months.months(getValue()); 218 } 219 220 //----------------------------------------------------------------------- 221 /** 222 * Gets the duration field type, which is <code>months</code>. 223 * 224 * @return the period type 225 */ 226 public DurationFieldType getFieldType() { 227 return DurationFieldType.months(); 228 } 229 230 /** 231 * Gets the period type, which is <code>months</code>. 232 * 233 * @return the period type 234 */ 235 public PeriodType getPeriodType() { 236 return PeriodType.months(); 237 } 238 239 //----------------------------------------------------------------------- 240 /** 241 * Gets the number of months that this period represents. 242 * 243 * @return the number of months in the period 244 */ 245 public int getMonths() { 246 return getValue(); 247 } 248 249 //----------------------------------------------------------------------- 250 /** 251 * Returns a new instance with the specified number of months added. 252 * <p> 253 * This instance is immutable and unaffected by this method call. 254 * 255 * @param months the amount of months to add, may be negative 256 * @return the new period plus the specified number of months 257 * @throws ArithmeticException if the result overflows an int 258 */ 259 public Months plus(int months) { 260 if (months == 0) { 261 return this; 262 } 263 return Months.months(FieldUtils.safeAdd(getValue(), months)); 264 } 265 266 /** 267 * Returns a new instance with the specified number of months added. 268 * <p> 269 * This instance is immutable and unaffected by this method call. 270 * 271 * @param months the amount of months to add, may be negative, null means zero 272 * @return the new period plus the specified number of months 273 * @throws ArithmeticException if the result overflows an int 274 */ 275 public Months plus(Months months) { 276 if (months == null) { 277 return this; 278 } 279 return plus(months.getValue()); 280 } 281 282 //----------------------------------------------------------------------- 283 /** 284 * Returns a new instance with the specified number of months taken away. 285 * <p> 286 * This instance is immutable and unaffected by this method call. 287 * 288 * @param months the amount of months to take away, may be negative 289 * @return the new period minus the specified number of months 290 * @throws ArithmeticException if the result overflows an int 291 */ 292 public Months minus(int months) { 293 return plus(FieldUtils.safeNegate(months)); 294 } 295 296 /** 297 * Returns a new instance with the specified number of months taken away. 298 * <p> 299 * This instance is immutable and unaffected by this method call. 300 * 301 * @param months the amount of months to take away, may be negative, null means zero 302 * @return the new period minus the specified number of months 303 * @throws ArithmeticException if the result overflows an int 304 */ 305 public Months minus(Months months) { 306 if (months == null) { 307 return this; 308 } 309 return minus(months.getValue()); 310 } 311 312 //----------------------------------------------------------------------- 313 /** 314 * Returns a new instance with the months multiplied by the specified scalar. 315 * <p> 316 * This instance is immutable and unaffected by this method call. 317 * 318 * @param scalar the amount to multiply by, may be negative 319 * @return the new period multiplied by the specified scalar 320 * @throws ArithmeticException if the result overflows an int 321 */ 322 public Months multipliedBy(int scalar) { 323 return Months.months(FieldUtils.safeMultiply(getValue(), scalar)); 324 } 325 326 /** 327 * Returns a new instance with the months divided by the specified divisor. 328 * The calculation uses integer division, thus 3 divided by 2 is 1. 329 * <p> 330 * This instance is immutable and unaffected by this method call. 331 * 332 * @param divisor the amount to divide by, may be negative 333 * @return the new period divided by the specified divisor 334 * @throws ArithmeticException if the divisor is zero 335 */ 336 public Months dividedBy(int divisor) { 337 if (divisor == 1) { 338 return this; 339 } 340 return Months.months(getValue() / divisor); 341 } 342 343 //----------------------------------------------------------------------- 344 /** 345 * Returns a new instance with the months value negated. 346 * 347 * @return the new period with a negated value 348 * @throws ArithmeticException if the result overflows an int 349 */ 350 public Months negated() { 351 return Months.months(FieldUtils.safeNegate(getValue())); 352 } 353 354 //----------------------------------------------------------------------- 355 /** 356 * Is this months instance greater than the specified number of months. 357 * 358 * @param other the other period, null means zero 359 * @return true if this months instance is greater than the specified one 360 */ 361 public boolean isGreaterThan(Months other) { 362 if (other == null) { 363 return getValue() > 0; 364 } 365 return getValue() > other.getValue(); 366 } 367 368 /** 369 * Is this months instance less than the specified number of months. 370 * 371 * @param other the other period, null means zero 372 * @return true if this months instance is less than the specified one 373 */ 374 public boolean isLessThan(Months other) { 375 if (other == null) { 376 return getValue() < 0; 377 } 378 return getValue() < other.getValue(); 379 } 380 381 //----------------------------------------------------------------------- 382 /** 383 * Gets this instance as a String in the ISO8601 duration format. 384 * <p> 385 * For example, "P4M" represents 4 months. 386 * 387 * @return the value as an ISO8601 string 388 */ 389 public String toString() { 390 return "P" + String.valueOf(getValue()) + "M"; 391 } 392 393 }