Java日期处理工具类DateUtils详解

import java.sql.Timestamp; 
import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.Calendar; 
import java.util.Date; 
 
/** 
 * <日期时间处理工具类> 
 */ 
public class DateUtils { 
 
 /** 
 * Date format pattern this is often used. 
 */ 
 public static final String PATTERN_YMD = "yyyy-MM-dd"; 
 
 /** 
 * Date format pattern this is often used. 
 */ 
 public static final String PATTERN_YMDHMS="yyyy-MM-dd HH:mm:ss"; 
 
 /** 
 * Formats the given date according to the YMD pattern. 
 * 
 * @param date The date to format. 
 * @return An YMD formatted date string. 
 * 
 * @see #PATTERN_YMD 
 */ 
 public static String formatDate(Date date) { 
 return formatDate(date, PATTERN_YMD); 
 } 
 
 /** 
 * Formats the given date according to the specified pattern. The pattern 
 * must conform to that used by the {@link SimpleDateFormat simple date 
 * format} class. 
 * 
 * @param date The date to format. 
 * @param pattern The pattern to use for formatting the date. 
 * @return A formatted date string. 
 * 
 * @throws IllegalArgumentException If the given date pattern is invalid. 
 * 
 * @see SimpleDateFormat 
 */ 
 public static String formatDate(Date date, String pattern) { 
 if (date == null) 
  throw new IllegalArgumentException("date is null"); 
 if (pattern == null) 
  throw new IllegalArgumentException("pattern is null"); 
  
 SimpleDateFormat formatter = new SimpleDateFormat(pattern); 
 return formatter.format(date); 
 } 
 
 /** 
 * Parses a date value. The format used for parsing the date value are retrieved from 
 * the default PATTERN_YMD. 
 * 
 * @param dateValue the date value to parse 
 * 
 * @return the parsed date 
 * 
 * @throws IllegalArgumentException If the given dateValue is invalid. 
 */ 
 public static Date parseDate(String dateValue) { 
 return parseDate(dateValue, null); 
 } 
 
 /** 
 * Parses the date value using the given date format. 
 * 
 * @param dateValue the date value to parse 
 * @param dateFormat the date format to use 
 * 
 * @return the parsed date. if parse is failed , return null 
 * 
 * @throws IllegalArgumentException If the given dateValue is invalid. 
 */ 
 public static Date parseDate(String dateValue, String dateFormat) { 
 if (dateValue == null) { 
  throw new IllegalArgumentException("dateValue is null"); 
 } 
 if (dateFormat == null) { 
  dateFormat = PATTERN_YMD; 
 } 
  
 SimpleDateFormat df = new SimpleDateFormat(dateFormat); 
 Date result = null; 
 try { 
  result = df.parse(dateValue); 
 } 
 catch (ParseException pe) { 
  pe.printStackTrace();// 日期型字符串格式错误 
 } 
 return result; 
 } 
 
 /** 
 * Adds a number of years to a date returning a new object. 
 * The original date object is unchanged. 
 * 
 * @param date the date, not null 
 * @param amount the amount to add, may be negative 
 * @return the new date object with the amount added 
 * @throws IllegalArgumentException if the date is null 
 */ 
 public static Date addYears(Date date, int amount) { 
 return add(date, Calendar.YEAR, amount); 
 } 
 
 /** 
 * Adds a number of years to a timestamp returning a new object. 
 * The original timestamp object is unchanged. 
 * 
 * @param timestamp the timestamp, not null 
 * @param amount the amount to add, may be negative 
 * @return the new timestamp object with the amount added 
 * @throws IllegalArgumentException if the timestamp is null 
 */ 
 public static Timestamp addYears(Timestamp timestamp, int amount) { 
 return add(timestamp, Calendar.YEAR, amount); 
 } 
 
 //----------------------------------------------------------------------- 
 /** 
 * Adds a number of months to a date returning a new object. 
 * The original date object is unchanged. 
 * 
 * @param date the date, not null 
 * @param amount the amount to add, may be negative 
 * @return the new date object with the amount added 
 * @throws IllegalArgumentException if the date is null 
 */ 
 public static Date addMonths(Date date, int amount) { 
 return add(date, Calendar.MONTH, amount); 
 } 
 
 /** 
 * Adds a number of months to a timestamp returning a new object. 
 * The original timestamp object is unchanged. 
 * 
 * @param timestamp the timestamp, not null 
 * @param amount the amount to add, may be negative 
 * @return the new timestamp object with the amount added 
 * @throws IllegalArgumentException if the timestamp is null 
 */ 
 public static Timestamp addMonths(Timestamp timestamp, int amount) { 
 return add(timestamp, Calendar.MONTH, amount); 
 } 
 
 //----------------------------------------------------------------------- 
 /** 
 * Adds a number of days to a date returning a new object. 
 * The original date object is unchanged. 
 * 
 * @param date the date, not null 
 * @param amount the amount to add, may be negative 
 * @return the new date object with the amount added 
 * @throws IllegalArgumentException if the date is null 
 */ 
 public static Date addDays(Date date, int amount) { 
 return add(date, Calendar.DATE, amount); 
 } 
 
 /** 
 * Adds a number of days to a timestamp returning a new object. 
 * The original timestamp object is unchanged. 
 * 
 * @param timestamp the timestamp, not null 
 * @param amount the amount to add, may be negative 
 * @return the new timestamp object with the amount added 
 * @throws IllegalArgumentException if the timestamp is null 
 */ 
 public static Timestamp addDays(Timestamp timestamp, int amount) { 
 return add(timestamp, Calendar.DATE, amount); 
 } 
 
 //----------------------------------------------------------------------- 
 /** 
 * Adds a number of minutes to a timestamp returning a new object. 
 * The original timestamp object is unchanged. 
 * 
 * @param timestamp the timestamp, not null 
 * @param amount the amount to add, may be negative 
 * @return the new timestamp object with the amount added 
 * @throws IllegalArgumentException if the timestamp is null 
 */ 
 public static Timestamp addMinutes(Timestamp timestamp, int amount) { 
 return add(timestamp, Calendar.MINUTE, amount); 
 } 
 
 /** 
 * Adds a number of days to current time returning a new object. 
 * 
 * @param amount the amount to add, may be negative 
 * @return the new timestamp object with the amount added 
 */ 
 public static Timestamp addDays(int amount) { 
 Calendar c = Calendar.getInstance(); 
 c.add(Calendar.DATE, amount); 
 return new Timestamp(c.getTimeInMillis()); 
 } 
 
 //----------------------------------------------------------------------- 
 /** 
 * Adds to a date returning a new object. 
 * The original date object is unchanged. 
 * 
 * @param date the date, not null 
 * @param calendarField the calendar field to add to 
 * @param amount the amount to add, may be negative 
 * @return the new date object with the amount added 
 * @throws IllegalArgumentException if the date is null 
 */ 
 private static Date add(Date date, int calendarField, int amount) { 
 if (date == null) { 
  throw new IllegalArgumentException("The date must not be null"); 
 } 
 Calendar c = Calendar.getInstance(); 
 c.setTime(date); 
 c.add(calendarField, amount); 
 return c.getTime(); 
 } 
 
 /** 
 * Adds to a timestamp returning a new object. 
 * The original timestamp object is unchanged. 
 * 
 * @param timestamp the timestamp, not null 
 * @param calendarField the calendar field to add to 
 * @param amount the amount to add, may be negative 
 * @return the new timestamp object with the amount added 
 * @throws IllegalArgumentException if the timestamp is null 
 */ 
 private static Timestamp add(Timestamp timestamp, int calendarField, int amount) { 
 if (timestamp == null) { 
  throw new IllegalArgumentException("The timestamp must not be null"); 
 } 
 Calendar c = Calendar.getInstance(); 
 c.setTime(timestamp); 
 c.add(calendarField, amount); 
 return new Timestamp(c.getTimeInMillis()); 
 } 
 
 /** 
 * <生成最小的当天日期值> 
 * @return 最小的当天日期值 
 */ 
 public static Timestamp now() { 
 Calendar c = Calendar.getInstance(); 
 c.set(Calendar.HOUR_OF_DAY, 0); 
 c.set(Calendar.MINUTE, 0); 
 c.set(Calendar.SECOND, 0); 
 c.set(Calendar.MILLISECOND, 0); 
 return new Timestamp(c.getTimeInMillis()); 
 } 
 
 
 
 /** This class should not be instantiated. */ 
 private DateUtils() { 
 } 
}