public abstract class Calendar implements Serializable, Cloneable, Comparable<Calendar> {}

public static Calendar getInstance()
{
 // 調(diào)用createCalendar()創(chuàng)建日歷
 Calendar cal = createCalendar(TimeZone.getDefaultRef(), Locale.getDefault());
 cal.sharedZone = true;
 return cal;
}


public static Calendar getInstance(TimeZone zone)
{
 // 調(diào)用createCalendar()創(chuàng)建日歷
 return createCalendar(zone, Locale.getDefault());
}


public static Calendar getInstance(Locale aLocale) {
 // 調(diào)用createCalendar()創(chuàng)建日歷
 Calendar cal = createCalendar(TimeZone.getDefaultRef(), aLocale);
 cal.sharedZone = true;
 return cal;
}

public static Calendar getInstance(TimeZone zone,
   Locale aLocale)
{
 // 調(diào)用createCalendar()創(chuàng)建日歷
 return createCalendar(zone, aLocale);
}

private static Calendar createCalendar(TimeZone zone,
   Locale aLocale)
{
 // (01) 若地區(qū)是“th”，則返回BuddhistCalendar對(duì)象
 // (02) 若地區(qū)是“JP”，則返回JapaneseImperialCalendar對(duì)象
 if ("th".equals(aLocale.getLanguage())
 && ("TH".equals(aLocale.getCountry()))) {
 return new sun.util.BuddhistCalendar(zone, aLocale);
 } else if ("JP".equals(aLocale.getVariant())
 && "JP".equals(aLocale.getCountry())
 && "ja".equals(aLocale.getLanguage())) {
 return new JapaneseImperialCalendar(zone, aLocale);
 } 

 // (03) 否則，返回GregorianCalendar對(duì)象
 return new GregorianCalendar(zone, aLocale); 
}

// time 是當(dāng)前時(shí)間，單位是毫秒。
// 它是當(dāng)前時(shí)間距離“January 1, 1970, 0:00:00 GMT”的差值。
protected long time;

// 保存這17個(gè)字段的數(shù)組
protected int  fields[];
// 數(shù)組的定義函數(shù)
protected Calendar(TimeZone zone, Locale aLocale)
{
 // 初始化“fields數(shù)組”
 fields = new int[FIELD_COUNT];
 isSet = new boolean[FIELD_COUNT];
 stamp = new int[FIELD_COUNT];

 this.zone = zone;
 setWeekCountData(aLocale);
}

public int get(int field) {
 // 計(jì)算各個(gè)字段的值
 complete();
 // 返回field字段的值
 return internalGet(field);
}

protected void complete()
{
 if (!isTimeSet)
 updateTime();
 if (!areFieldsSet || !areAllFieldsSet) {
 computeFields(); // fills in unset fields
 areAllFieldsSet = areFieldsSet = true;
 }
}
private void updateTime() {
 computeTime();
 isTimeSet = true;
}
updateTime() 調(diào)用到的 computeTime() 定義在 Calendar.java的實(shí)現(xiàn)類中。下面，我列出GregorianCalendar.java中computeTime()的實(shí)現(xiàn)：
protected void computeTime() {
 // In non-lenient mode, perform brief checking of calendar
 // fields which have been set externally. Through this
 // checking, the field values are stored in originalFields[]
 // to see if any of them are normalized later.
 if (!isLenient()) {
 if (originalFields == null) {
  originalFields = new int[FIELD_COUNT];
 }
 for (int field = 0; field < FIELD_COUNT; field++) {
  int value = internalGet(field);
  if (isExternallySet(field)) {
  // Quick validation for any out of range values
  if (value < getMinimum(field) || value > getMaximum(field)) {
   throw new IllegalArgumentException(getFieldName(field));
  }
  }
  originalFields[field] = value;
 }
 }

 // Let the super class determine which calendar fields to be
 // used to calculate the time.
 int fieldMask = selectFields();

 // The year defaults to the epoch start. We don't check
 // fieldMask for YEAR because YEAR is a mandatory field to
 // determine the date.
 int year = isSet(YEAR) ? internalGet(YEAR) : EPOCH_YEAR;

 int era = internalGetEra();
 if (era == BCE) {
 year = 1 - year;
 } else if (era != CE) {
 // Even in lenient mode we disallow ERA values other than CE & BCE.
 // (The same normalization rule as add()/roll() could be
 // applied here in lenient mode. But this checking is kept
 // unchanged for compatibility as of 1.5.)
 throw new IllegalArgumentException("Invalid era");
 }

 // If year is 0 or negative, we need to set the ERA value later.
 if (year <= 0 && !isSet(ERA)) {
 fieldMask |= ERA_MASK;
 setFieldsComputed(ERA_MASK);
 }

 // Calculate the time of day. We rely on the convention that
 // an UNSET field has 0.
 long timeOfDay = 0;
 if (isFieldSet(fieldMask, HOUR_OF_DAY)) {
 timeOfDay += (long) internalGet(HOUR_OF_DAY);
 } else {
 timeOfDay += internalGet(HOUR);
 // The default value of AM_PM is 0 which designates AM.
 if (isFieldSet(fieldMask, AM_PM)) {
  timeOfDay += 12 * internalGet(AM_PM);
 }
 }
 timeOfDay *= 60;
 timeOfDay += internalGet(MINUTE);
 timeOfDay *= 60;
 timeOfDay += internalGet(SECOND);
 timeOfDay *= 1000;
 timeOfDay += internalGet(MILLISECOND);

 // Convert the time of day to the number of days and the
 // millisecond offset from midnight.
 long fixedDate = timeOfDay / ONE_DAY;
 timeOfDay %= ONE_DAY;
 while (timeOfDay < 0) {
 timeOfDay += ONE_DAY;
 --fixedDate;
 }

 // Calculate the fixed date since January 1, 1 (Gregorian).
 calculateFixedDate: {
 long gfd, jfd;
 if (year > gregorianCutoverYear && year > gregorianCutoverYearJulian) {
  gfd = fixedDate + getFixedDate(gcal, year, fieldMask);
  if (gfd >= gregorianCutoverDate) {
  fixedDate = gfd;
  break calculateFixedDate;
  }
  jfd = fixedDate + getFixedDate(getJulianCalendarSystem(), year, fieldMask);
 } else if (year < gregorianCutoverYear && year < gregorianCutoverYearJulian) {
  jfd = fixedDate + getFixedDate(getJulianCalendarSystem(), year, fieldMask);
  if (jfd < gregorianCutoverDate) {
  fixedDate = jfd;
  break calculateFixedDate;
  }
  gfd = fixedDate + getFixedDate(gcal, year, fieldMask);
 } else {
  gfd = fixedDate + getFixedDate(gcal, year, fieldMask);
  jfd = fixedDate + getFixedDate(getJulianCalendarSystem(), year, fieldMask);
 }
 // Now we have to determine which calendar date it is.
 if (gfd >= gregorianCutoverDate) {
  if (jfd >= gregorianCutoverDate) {
  fixedDate = gfd;
  } else {
  // The date is in an "overlapping" period. No way
  // to disambiguate it. Determine it using the
  // previous date calculation.
  if (calsys == gcal || calsys == null) {
   fixedDate = gfd;
  } else {
   fixedDate = jfd;
  }
  }
 } else {
  if (jfd < gregorianCutoverDate) {
  fixedDate = jfd;
  } else {
  // The date is in a "missing" period.
  if (!isLenient()) {
   throw new IllegalArgumentException("the specified date doesn't exist");
  }
  // Take the Julian date for compatibility, which
  // will produce a Gregorian date.
  fixedDate = jfd;
  }
 }
 }

 // millis represents local wall-clock time in milliseconds.
 long millis = (fixedDate - EPOCH_OFFSET) * ONE_DAY + timeOfDay;

 // Compute the time zone offset and DST offset. There are two potential
 // ambiguities here. We'll assume a 2:00 am (wall time) switchover time
 // for discussion purposes here.
 // 1. The transition into DST. Here, a designated time of 2:00 am - 2:59 am
 // can be in standard or in DST depending. However, 2:00 am is an invalid
 // representation (the representation jumps from 1:59:59 am Std to 3:00:00 am DST).
 // We assume standard time.
 // 2. The transition out of DST. Here, a designated time of 1:00 am - 1:59 am
 // can be in standard or DST. Both are valid representations (the rep
 // jumps from 1:59:59 DST to 1:00:00 Std).
 // Again, we assume standard time.
 // We use the TimeZone object, unless the user has explicitly set the ZONE_OFFSET
 // or DST_OFFSET fields; then we use those fields.
 TimeZone zone = getZone();
 if (zoneOffsets == null) {
 zoneOffsets = new int[2];
 }
 int tzMask = fieldMask & (ZONE_OFFSET_MASK|DST_OFFSET_MASK);
 if (tzMask != (ZONE_OFFSET_MASK|DST_OFFSET_MASK)) {
 if (zone instanceof ZoneInfo) {
  ((ZoneInfo)zone).getOffsetsByWall(millis, zoneOffsets);
 } else {
  int gmtOffset = isFieldSet(fieldMask, ZONE_OFFSET) ?
  internalGet(ZONE_OFFSET) : zone.getRawOffset();
  zone.getOffsets(millis - gmtOffset, zoneOffsets);
 }
 }
 if (tzMask != 0) {
 if (isFieldSet(tzMask, ZONE_OFFSET)) {
  zoneOffsets[0] = internalGet(ZONE_OFFSET);
 }
 if (isFieldSet(tzMask, DST_OFFSET)) {
  zoneOffsets[1] = internalGet(DST_OFFSET);
 }
 }

 // Adjust the time zone offset values to get the UTC time.
 millis -= zoneOffsets[0] + zoneOffsets[1];

 // Set this calendar's time in milliseconds
 time = millis;

 int mask = computeFields(fieldMask | getSetStateFields(), tzMask);

 if (!isLenient()) {
 for (int field = 0; field < FIELD_COUNT; field++) {
  if (!isExternallySet(field)) {
  continue;
  }
  if (originalFields[field] != internalGet(field)) {
  // Restore the original field values
  System.arraycopy(originalFields, 0, fields, 0, fields.length);
  throw new IllegalArgumentException(getFieldName(field));
  }
 }
 }
 setFieldsNormalized(mask);
}

protected final int internalGet(int field) {
 return fields[field];
}

// 獲取Calendar實(shí)例
Calendar cal = Calendar.getInstance();
// 獲取MONTH的最大值
int max = cal.getMaximum(Calendar.MONTH);

// 獲取Calendar實(shí)例
Calendar cal = Calendar.getInstance();
// 獲取當(dāng)前MONTH的最大值
int max = cal.getActualMaximum(Calendar.MONTH);

// 獲取Calendar實(shí)例
Calendar cal = Calendar.getInstance();
// 獲取MONTH的最小值
int min = cal.getMinimum(Calendar.MONTH);

作用：獲取“當(dāng)前日期下，該字段的最小值”。 示例：以“MONTH”字段來說。使用方法為：
// 獲取Calendar實(shí)例
Calendar cal = Calendar.getInstance();
// 獲取MONTH的最小值
int min = cal.getMinimum(Calendar.MONTH);

// 獲取Calendar實(shí)例
Calendar cal = Calendar.getInstance();
// 獲取“cal日歷”的當(dāng)前MONTH值
int MONTH = cal.get(Calendar.MONTH);

// 獲取Calendar實(shí)例
Calendar cal = Calendar.getInstance();
// 設(shè)置“cal日歷”的當(dāng)前MONTH值為 1988年
cal.set(Calendar.MONTH, 1988);

// 獲取Calendar實(shí)例，并設(shè)置日期為“2013-09-01”
Calendar cal = Calendar.getInstance();
cal.set(Calendar.YEAR, 2013);
cal.set(Calendar.MONTH, 8);
cal.set(Calendar.DATE, 1);
// 給“cal日歷”的當(dāng)前MONTH值 “添加-10”
cal.add(Calendar.MONTH, -10);

// 獲取Calendar實(shí)例，并設(shè)置日期為“2013-09-01”
Calendar cal = Calendar.getInstance();
cal.set(Calendar.YEAR, 2013);
cal.set(Calendar.MONTH, 8);
cal.set(Calendar.DATE, 1);
// 將“cal日歷”的當(dāng)前MONTH值 “向前滾動(dòng)10”
cal.roll(Calendar.MONTH, -10);

// 獲取Calendar實(shí)例，并設(shè)置日期為“9月”
Calendar cal = Calendar.getInstance();
cal.set(Calendar.MONTH, 9);
// 清空MONTH
cal.clear(Calendar.MONTH);

// 獲取Calendar實(shí)例
Calendar cal = Calendar.getInstance();
// 判斷MONTH是否被設(shè)置
boolean bset = cal.isSet(Calendar.MONTH);

// 比較“當(dāng)前Calendar對(duì)象”和“calendar” 的日期、時(shí)區(qū)等內(nèi)容是否相等。
boolean equals(Object object)
// 當(dāng)前Calendar對(duì)象 是否 早于calendar
boolean before(Object calendar)
// 當(dāng)前Calendar對(duì)象 是否 晚于calendar
boolean after(Object calendar)
// 比較“當(dāng)前Calendar對(duì)象”和“calendar”。
// 若 早于 “calendar” 則，返回-1
// 若 相等， 則，返回0
// 若 晚于 “calendar” 則，返回1
int compareTo(Calendar anotherCalendar) 

// 它們的使用方法如下
boolean isEqual = cal1.equals(cal2);
boolean isBefore = cal1.before(cal2);
boolean isAfter = cal1.after(cal2);
int icompare = cal1.compareTo(cal2);

// 設(shè)置“Calendar的寬容度”
void setLenient(boolean value)
// 獲取“Calendar的寬容度”
boolean isLenient()

// 設(shè)置“年月日”
final void set(int year, int month, int day)
// 設(shè)置“年月日時(shí)分”
final void set(int year, int month, int day, int hourOfDay, int minute, int second)
// 設(shè)置“年月日時(shí)分秒”
final void set(int year, int month, int day, int hourOfDay, int minute)
// 獲取Calendar對(duì)應(yīng)的日期
final Date getTime()
// 設(shè)置Calendar為date
final void setTime(Date date)
// 獲取Calendar對(duì)應(yīng)的時(shí)區(qū)
TimeZone getTimeZone()
// 設(shè)置Calendar對(duì)應(yīng)的時(shí)區(qū)
void setTimeZone(TimeZone timezone)
// 獲取Calendar對(duì)應(yīng)的milliscondes值，就是“Calendar當(dāng)前日期”距離“1970-01-01 0:00:00 GMT”的毫秒數(shù)
long getTimeInMillis()
// 設(shè)置Calendar對(duì)應(yīng)的milliscondes值
void setTimeInMillis(long milliseconds)

// 克隆Calendar
Object clone()
// 獲取“每周的第一天是星期幾”。例如，在美國(guó)，這一天是 SUNDAY，而在法國(guó)，這一天是 MONDAY。
int getFirstDayOfWeek()
// 設(shè)置“每周的第一天是星期幾”。例如，在美國(guó)，這一天是 SUNDAY，而在法國(guó)，這一天是 MONDAY。
void setFirstDayOfWeek(int value)
// 獲取一年中第一個(gè)星期所需的最少天數(shù)，例如，如果定義第一個(gè)星期包含一年第一個(gè)月的第一天，則此方法將返回 1。如果最少天數(shù)必須是一整個(gè)星期，則此方法將返回 7。
int getMinimalDaysInFirstWeek()
// 設(shè)置一年中第一個(gè)星期所需的最少天數(shù)，例如，如果定義第一個(gè)星期包含一年第一個(gè)月的第一天，則使用值 1 調(diào)用此方法。如果最少天數(shù)必須是一整個(gè)星期，則使用值 7 調(diào)用此方法。
void setMinimalDaysInFirstWeek(int value)

import java.util.Date;
import java.util.Calendar;
import java.util.TimeZone;
import java.util.Random;

public class CalendarTest {

 public static void main(String[] args) {

 // 測(cè)試Calendar的“17個(gè)字段的公共函數(shù)接口”
 testAllCalendarSections() ;

 // 測(cè)試Calendar的“比較接口”
 testComparatorAPIs() ;

 // 測(cè)試Calendar的“比較接口”
 testLenientAPIs() ;

 // 測(cè)試Calendar的Date、TimeZone、MilliSecond等相關(guān)函數(shù)
 testTimeAPIs() ;

 // 測(cè)試Calendar的clone()，getFirstDayOfWeek()等接口
 testOtherAPIs() ;

 }


 /**
 * 測(cè)試“Calendar的字段”
 *
 * @param cal -- Calendar對(duì)象
 * @param field -- 要測(cè)試的“Calendar字段”?？梢詾橐韵轮担?
 * Calendar.YEAR, Calendar.MONTH, Calendar.DATE, ... 等等
 * @param title -- 標(biāo)題
 */
 private static void testSection(Calendar cal, int field, String title) {
 final Random random = new Random();
 final Date date = cal.getTime();

 final int min = cal.getMinimum(field); // 獲取"字段最小值"
 final int max = cal.getMaximum(field); // 獲取“字段最大值”

 final int actualMin = cal.getActualMinimum(field); // 獲取"當(dāng)前日期下，該字段最小值"
 final int actualMax = cal.getActualMaximum(field); // 獲取“當(dāng)前日期下，該字段的最大值”

 // 獲取“字段的當(dāng)前值”
 final int ori = cal.get(field);  

 // 設(shè)置“字段的當(dāng)前值”, 并獲取“設(shè)置之后的值”
 final int r1 = random.nextInt(max);
 cal.set(field, r1);  
 final int set = cal.get(field);  
 try {
  // 回滾“字段的當(dāng)前值”：在“字段最小值”和“字段最大值”之間回滾。
  // “回滾值”可以為正，也可以為負(fù)。
  cal.roll(field, -max);  
 } catch (IllegalArgumentException e) {
  // 當(dāng)field == Calendar.ZONE_OFFSET時(shí)，會(huì)拋出該異常！
  e.printStackTrace();
 }
 final int roll = cal.get(field);  

 // 獲取一個(gè)隨機(jī)值
 final int sign = ( random.nextInt(2) == 1) ? 1 : -1;
 final int r2 = sign * random.nextInt(max);
 try {
  // 增加“字段的當(dāng)前值” ，并獲取“新的當(dāng)前字段值”
  // add的“參數(shù)值”可以為正，也可以為負(fù)。
  cal.add(field, r2);  
 } catch (IllegalArgumentException e) {
  // 當(dāng)field == Calendar.ZONE_OFFSET時(shí)，會(huì)拋出該異常！
  e.printStackTrace();
 }
 final int add = cal.get(field);



 // 打印字段信息
 System.out.printf("%s:\n\trange is [%d - %d] actualRange is [%d - %d]. original=%d, set(%d)=%d, roll(%d)=%d, add(%d)=%d\n",
  title, min, max, actualMin, actualMax, ori, r1, set, -max, roll, r2, add);
 }

 /**
 * 測(cè)試Calendar的“17個(gè)字段的公共函數(shù)接口”
 */
 private static void testAllCalendarSections() {
 // 00. ERA 字段
 testSection(Calendar.getInstance(), Calendar.ERA, "Calendar.ERA");
 // 01. YEAR 字段
 testSection(Calendar.getInstance(), Calendar.YEAR, "Calendar.YEAR");
 // 02. MONTH 字段
 testSection(Calendar.getInstance(), Calendar.MONTH, "Calendar.MONTH");
 // 03. WEEK_OF_YEAR 字段
 testSection(Calendar.getInstance(), Calendar.WEEK_OF_YEAR, "Calendar.WEEK_OF_YEAR");
 // 04. WEEK_OF_MONTH 字段
 testSection(Calendar.getInstance(), Calendar.WEEK_OF_MONTH, "Calendar.WEEK_OF_MONTH");
 // 05. DATE 字段
 testSection(Calendar.getInstance(), Calendar.DATE, "Calendar.DATE");
 // 06. DAY_OF_MONTH 字段
 testSection(Calendar.getInstance(), Calendar.DAY_OF_MONTH, "Calendar.DAY_OF_MONTH");
 // 07. DAY_OF_YEAR 字段
 testSection(Calendar.getInstance(), Calendar.DAY_OF_YEAR, "Calendar.DAY_OF_YEAR");
 // 08. DAY_OF_WEEK 字段
 testSection(Calendar.getInstance(), Calendar.DAY_OF_WEEK, "Calendar.DAY_OF_WEEK");
 // 09. DAY_OF_WEEK_IN_MONTH 字段
 testSection(Calendar.getInstance(), Calendar.DAY_OF_WEEK_IN_MONTH, "Calendar.DAY_OF_WEEK_IN_MONTH");
 // 10. AM_PM 字段
 testSection(Calendar.getInstance(), Calendar.AM_PM, "Calendar.AM_PM");
 // 11. HOUR 字段
 testSection(Calendar.getInstance(), Calendar.HOUR, "Calendar.HOUR");
 // 12. HOUR_OF_DAY 字段
 testSection(Calendar.getInstance(), Calendar.HOUR_OF_DAY, "Calendar.HOUR_OF_DAY");
 // 13. MINUTE 字段
 testSection(Calendar.getInstance(), Calendar.MINUTE, "Calendar.MINUTE");
 // 14. SECOND 字段
 testSection(Calendar.getInstance(), Calendar.SECOND, "Calendar.SECOND");
 // 15. MILLISECOND 字段
 testSection(Calendar.getInstance(), Calendar.MILLISECOND, "Calendar.MILLISECOND");
 // 16. ZONE_OFFSET 字段
 testSection(Calendar.getInstance(), Calendar.ZONE_OFFSET, "Calendar.ZONE_OFFSET");
 }

 /**
 * 測(cè)試Calendar的“比較接口”
 */
 private static void testComparatorAPIs() {
 // 新建cal1 ，且時(shí)間為1988年
 Calendar cal1 = Calendar.getInstance();
 cal1.set(Calendar.YEAR, 1988);
 // 新建cal2 ，且時(shí)間為2000年
 Calendar cal2 = Calendar.getInstance();
 cal2.set(Calendar.YEAR, 2000);
 // 新建cal3, 為cal1的克隆對(duì)象
 Calendar cal3 = (Calendar)cal1.clone();

 // equals 判斷 cal1和cal2的“時(shí)間、時(shí)區(qū)等”內(nèi)容是否相等
 boolean isEqual12 = cal1.equals(cal2);
 // equals 判斷 cal1和cal3的“時(shí)間、時(shí)區(qū)等”內(nèi)容是否相等
 boolean isEqual13 = cal1.equals(cal3);
 // cal1是否比cal2早
 boolean isBefore = cal1.before(cal2);
 // cal1是否比cal2晚
 boolean isAfter = cal1.after(cal2);
 // 比較cal1和cal2
 // (01) 若cal1 早于 cal2，返回-1
 // (02) 若cal1 等于 cal2，返回0
 // (03) 若cal1 晚于 cal2，返回1
 int icompare = cal1.compareTo(cal2);

 System.out.printf("\ntestComparatorAPIs: isEuqal12=%s, isEqual13=%s, isBefore=%s, isAfter=%s, icompare=%s\n",
  isEqual12, isEqual13, isBefore, isAfter, icompare);
 }

 /**
 * 測(cè)試Calendar的“比較接口”
 */
 private static void testLenientAPIs() {
  Calendar cal = Calendar.getInstance();

  // 獲取默認(rèn)的“寬容度”。返回true
  boolean oriLenient = cal.isLenient();
  // MONTH值只能是“0-11”，這里越界。但是由于當(dāng)前cal是寬容的，所以不會(huì)拋出異常
  cal.set(Calendar.MONTH, 50); 

  // 設(shè)置“寬容度”為false。
  cal.setLenient(false);
  // 獲取設(shè)置后的“寬容度”
  boolean curLenient = cal.isLenient();
  try {
  // MONTH值只能是“0-11”，這里越界。而且當(dāng)前cal是不寬容的，所以會(huì)產(chǎn)生異常。
  // 但是，異常到下次計(jì)算日期時(shí)才會(huì)拋出。即，set()中不回拋出異常，而要等到get()中才會(huì)拋出異常
  cal.set(Calendar.MONTH, 50);
  // 此時(shí)，對(duì)cal進(jìn)行讀取。讀取會(huì)導(dǎo)致重新計(jì)算cal的值，所以此時(shí)拋出異常！
  int m2 = cal.get(Calendar.MONTH); 
 } catch (IllegalArgumentException e) {
  e.printStackTrace();
 }

 System.out.printf("\ntestLenientAPIs: oriLenient=%s, curLenient=%s\n",
  oriLenient, curLenient);
 }

 /**
 * 測(cè)試Calendar的Date、TimeZone、MilliSecond等相關(guān)函數(shù)
 */
 private static void testTimeAPIs() {
 Calendar cal = Calendar.getInstance();

 // 設(shè)置cal的時(shí)區(qū)為“GMT+8”
 cal.setTimeZone(TimeZone.getTimeZone("GMT+8"));
 // 獲取當(dāng)前的cal時(shí)區(qū)
 TimeZone timezone = cal.getTimeZone();

 // 設(shè)置 milliseconds
 cal.setTimeInMillis(1279419645742l);
 // 獲取 milliseconds
 long millis = cal.getTimeInMillis();
 // 設(shè)置 milliseconds之后，時(shí)間也改變了。
 // 獲取cal對(duì)應(yīng)的日期
 Date date = cal.getTime();

 // 設(shè)置時(shí)間為“1988-08-08”
 cal.set(1988, 08, 08);
 // 設(shè)置時(shí)間為“1999-09-09 09:09”
 cal.set(1999, 09, 09, 9, 9);
 // 設(shè)置時(shí)間為“2000-10-10 10:10:10”
 cal.set(2000, 10, 10, 10, 10, 10);

 System.out.printf("\ntestTimeAPIs: date=%s, timezone=%s, millis=%s\n",
  date, timezone, millis);
 }

 /**
 * 測(cè)試Calendar的clone()，getFirstDayOfWeek()等接口
 */
 private static void testOtherAPIs() {
 Calendar cal = Calendar.getInstance();
 // 克隆cal
 Calendar clone = (Calendar)cal.clone();

 // 設(shè)置 為 2013-01-10。 
 // 注：2013-01-01 為“星期二”，2013-01-06為“星期天”，
 clone.set(Calendar.YEAR, 2013);
 clone.set(Calendar.MONTH, 0);
 clone.set(Calendar.DATE, 10);
 // 設(shè)置“本年的第一個(gè)星期最少包含1天”。
 // 則2013-01-10屬于第2個(gè)星期
 clone.setMinimalDaysInFirstWeek(1);
 int m1 = clone.getMinimalDaysInFirstWeek();
 int index1 = clone.get(Calendar.WEEK_OF_YEAR);

 // 設(shè)置“本年的第一個(gè)星期最少包含7天”。
 // 則2013-01-10屬于第1個(gè)星期
 clone.setMinimalDaysInFirstWeek(7);
 int m2 = clone.getMinimalDaysInFirstWeek();
 int index2 = clone.get(Calendar.WEEK_OF_YEAR);

 // 設(shè)置“每周的第一天是星期幾”。
 clone.setFirstDayOfWeek(Calendar.WEDNESDAY);
 // 獲取“每周的第一天是星期幾”。
 int firstdayOfWeek = clone.getFirstDayOfWeek();

 System.out.printf("\ntestOtherAPIs: firstdayOfWeek=%s, [minimalDay, WeekOfYear]={(%s, %s), (%s, %s)} %s\n",
  firstdayOfWeek, m1, index1, m2, index2, clone.getTime());
 }
}

import java.util.Calendar;

/**
 * 根據(jù)Calendar的API封裝的一些常用函數(shù)
 */
public class CalendarSelfDefineTest {

 public static void main(String[] args) {
 Calendar cal = Calendar.getInstance();

 // 設(shè)置日期為“2013-09-18”
 cal.set(2013, Calendar.SEPTEMBER, 18);

 // 獲取“年”
 System.out.printf("year: %s\n", getYear(cal) );
 // 獲取“月”
 System.out.printf("month: %s\n", getMonth(cal) );
 // 獲取“上月”
 System.out.printf("previcou month: %s\n", getLastMonth(cal) );
 // 獲取“下月”
 System.out.printf("next month: %s\n", getNextMonth(cal) );
 // 獲取“日”
 System.out.printf("day: %s\n", getDay(cal) );
 // 獲取Cal對(duì)應(yīng)星期幾
 System.out.printf("weekday: %s\n", getWeekDay(cal) );
 // 本月天數(shù)
 System.out.printf("Current Month days: %s\n", getMonthDays(cal) );
 // 上月天數(shù)
 System.out.printf("Previcous Month days: %s\n", getPrevMonthDays(cal) );
 // 下月天數(shù)
 System.out.printf("Next Month days: %s\n", getNextMonthDays(cal) );
 // 獲取當(dāng)月第一天的星期幾
 System.out.printf("First day' weekday : %s\n", getFirstDayWeekday(cal) );
 // 獲取當(dāng)前月最后一天的星期幾
 System.out.printf("Last day' weekday : %s\n", getLastDayWeekday(cal) );
 // 獲取上月最后一天的星期幾
 System.out.printf("PrevMonth Last day' weekday: %s\n", getLastDayWeekdayOfPrevMonth(cal) );
 // 獲取下月第一天的星期幾
 System.out.printf("NextMonth First day' weekday: %s\n", getFirstDayWeekdayOfNextMonth(cal) );
 }

 /**
 * 獲取“年”
 * 
 * @return 例如，2013-09-18，則返回2013
 */
 public static int getYear(Calendar cal) {
 return cal.get(Calendar.YEAR);
 } 

 /**
 * 獲取“月”
 * 
 * @return 返回值可以為以下值：
 * JANUARY, FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER, UNDECIMBER。
 * 其中第一個(gè)月是 JANUARY，它為 0。
 *
 * 例如，2013-09-18，則返回8
 */
 public static int getMonth(Calendar cal) {
 return cal.get(Calendar.MONTH);
 } 

 /**
 * 獲取“上一個(gè)月”
 * 
 * @return 返回值可以為以下值：
 * JANUARY, FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER, UNDECIMBER。
 * 其中第一個(gè)月是 JANUARY，它為 0。
 *
 * 例如，2012-01-12的上一個(gè)月是“11”(即DECEMBER)。
 */
 public static int getLastMonth(Calendar cal) {
 return (cal.get(Calendar.MONTH) + 11) % 12;
 } 

 /**
 * 獲取“下一個(gè)月”
 * 
 * @return 返回值可以為以下值：
 * JANUARY, FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER, UNDECIMBER。
 * 其中第一個(gè)月是 JANUARY，它為 0。
 *
 * 例如，2013-12-12的下一個(gè)月是“1”(即DECEMBER)。
 */
 public static int getNextMonth(Calendar cal) {
 return (cal.get(Calendar.MONTH) + 13) % 12;
 } 

 /**
 * 獲取“日”
 *
 * @return 例如，2013-09-18，則返回18
 *
 */
 public static int getDay(Calendar cal) {
 return cal.get(Calendar.DATE);
 } 

 /**
 * 獲取“本月的天數(shù)”
 *
 * @return 例如，2013-09-18，則返回30
 *
 */
 public static int getMonthDays(Calendar cal) {
 return cal.getActualMaximum(Calendar.DATE); 
 } 

 /**
 * 獲取“上一個(gè)月的天數(shù)”
 *
 * @return 例如，2013-01-18，則返回31 (因?yàn)?012-12有31天)
 *
 */
 public static int getPrevMonthDays(Calendar cal) {
 Calendar tmpCal = (Calendar)cal.clone(); // 克隆cal。后面對(duì)tmpCal操作，就不會(huì)改變cal
 tmpCal.add(Calendar.MONTH, -1);   // 設(shè)為“上一個(gè)月”
 return tmpCal.getActualMaximum(Calendar.DATE); 
 } 

 /**
 * 獲取“下一個(gè)月的天數(shù)”
 *
 * @return 例如，2013-12-18，則返回31 (因?yàn)?014-01有31天)
 *
 */
 public static int getNextMonthDays(Calendar cal) {
 Calendar tmpCal = (Calendar)cal.clone(); // 克隆cal。后面對(duì)tmpCal操作，就不會(huì)改變cal
 tmpCal.add(Calendar.MONTH, 1);   // 設(shè)為“下一個(gè)月”
 return tmpCal.getActualMaximum(Calendar.DATE); 
 } 

 /**
 * 獲取Cal對(duì)應(yīng)星期幾
 *
 * @return 返回“星期幾”，可以為以下值：
 * SUNDAY、MONDAY、TUESDAY、WEDNESDAY、THURSDAY、FRIDAY 和 SATURDAY。
 * SUNDAY為1，MONDAY為2，依次類推。
 * 例如，2013-09-18(星期三)，則返回4
 */
 public static int getWeekDay(Calendar cal) {
 return cal.get(Calendar.DAY_OF_WEEK);
 } 


 /**
 * 獲取當(dāng)月第一天對(duì)應(yīng)星期幾
 *
 * @return SUNDAY為1，MONDAY為2，依次類推。
 */
 public static int getFirstDayWeekday(Calendar cal) {

 Calendar tmpCal = (Calendar)cal.clone(); // 克隆cal。后面對(duì)tmpCal操作，就不會(huì)改變cal
 tmpCal.set(Calendar.DATE, 1);   // 把日期設(shè)置為當(dāng)月第一天 
 return tmpCal.get(Calendar.DAY_OF_WEEK);
 } 

 /**
 * 獲取當(dāng)前月最后一天對(duì)應(yīng)星期幾
 * 
 * @return SUNDAY為1，MONDAY為2，依次類推。
 */
 public static int getLastDayWeekday(Calendar cal) {
 Calendar tmpCal = (Calendar)cal.clone(); // 克隆cal。后面對(duì)tmpCal操作，就不會(huì)改變cal
 tmpCal.set(Calendar.DATE, 1);   // 把日期設(shè)置為當(dāng)月第一天 
 tmpCal.roll(Calendar.DATE, -1);   // 把日期設(shè)置為當(dāng)月最后一天 
 return tmpCal.get(Calendar.DAY_OF_WEEK);
 } 


 /**
 * 獲取上月最后一天的星期幾
 * 
 * @return SUNDAY為1，MONDAY為2，依次類推。
 */
 public static int getLastDayWeekdayOfPrevMonth(Calendar cal) {

 Calendar tmpCal = (Calendar)cal.clone(); // 克隆cal。后面對(duì)tmpCal操作，就不會(huì)改變cal
 tmpCal.set(Calendar.DATE, 1);   // 把日期設(shè)置為當(dāng)月第一天 
 tmpCal.add(Calendar.DATE, -1);   // 把日期設(shè)置為上一個(gè)月最后一天 
 return tmpCal.get(Calendar.DAY_OF_WEEK);
 } 

 /**
 * 獲取下月第一天的星期偏移
 * 
 * @return SUNDAY為1，MONDAY為2，依次類推。
 */
 public static int getFirstDayWeekdayOfNextMonth(Calendar cal) {

 Calendar tmpCal = (Calendar)cal.clone(); // 克隆cal。后面對(duì)tmpCal操作，就不會(huì)改變cal
 tmpCal.add(Calendar.MONTH, 1);   // 設(shè)為“下一個(gè)月”
 tmpCal.set(Calendar.DATE, 1);   // 設(shè)為“第一天” 
 return tmpCal.get(Calendar.DAY_OF_WEEK);
 } 
}