java 日期计算

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.regex.Matcher;
import java.util.regex.Pattern;


public class DateUtil {
    
public static final String FormatDayToChinaTime24H = "yyyy年MM月dd日";
public static String DATETIME_FORMAT = "yyyy-MM-dd HH:mm:ss";
public static String DATE_FORMAT = "yyyy-MM-dd";
public static String TIME_FORMAT = "HH:mm:ss";

/**
* 返回年份
* 
* @param date
*            日期
* @return 返回年份
*/
public static int getYear(Date date) {
java.util.Calendar c = java.util.Calendar.getInstance();
c.setTime(date);
return c.get(java.util.Calendar.YEAR);
}


/**
* 返回月份
* 
* @param date
*            日期
* @return 返回月份
*/
public static int getMonth(Date date) {
java.util.Calendar c = java.util.Calendar.getInstance();
c.setTime(date);
return c.get(java.util.Calendar.MONTH) + 1;
}


/**
* 返回日份
* 
* @param date
*            日期
* @return 返回日份
*/
public static int getDay(Date date) {
java.util.Calendar c = java.util.Calendar.getInstance();
c.setTime(date);
return c.get(java.util.Calendar.DAY_OF_MONTH);
}

/**
* Parse date like "yyyy-MM-dd".
*/
public static Date parseDate(String d) {
try {
return new SimpleDateFormat(DATE_FORMAT).parse(d);
} catch (Exception e) {
}
return null;
}

/**
* Parse date like "yyyy-MM-dd HH:mm:ss".
*/
public static Date parseDateTime(String d) {
try {
return new SimpleDateFormat(DATETIME_FORMAT).parse(d);
} catch (Exception e) {
}
return null;
}

/**
* Parse date like "HH:mm:ss".
*/
public static Date parseTime(String d) {
try {
return new SimpleDateFormat(TIME_FORMAT).parse(d);
} catch (Exception e) {
}
return null;
}

/**
* 取得指定月份的最后一天
* 
* @param strdate
*            String
* @return String
*/
public String getMonthEnd(String strdate) {
Date date = parseDate(getMonthBegin(strdate));
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.MONTH, 1);
calendar.add(Calendar.DAY_OF_YEAR, -1);
return formatDate(calendar.getTime());
}

/**
* 取得指定月份的第一天
* 
* @param strdate
*            String
* @return String
*/
public String getMonthBegin(String strdate) {
Date date = parseDate(strdate);
return formatDateByFormat(date, "yyyy-MM") + "-01";
}

/**
* 以指定的格式来格式化日期
* 
* @param date
*            Date
* @param format
*            String
* @return String
*/
public static String formatDateByFormat(Date date, String format) {
String result = "";
if (date != null) {
try {
SimpleDateFormat sdf = new SimpleDateFormat(format);
result = sdf.format(date);
} catch (Exception ex) {
ex.printStackTrace();
}
}
return result;
}

/**
* 常用的格式化日期
* 
* @param date
*            Date
* @return String
*/
public String formatDate(Date date) {
return formatDateByFormat(date, "yyyy-MM-dd");
}

/**
* @根据当前日期计算n天后的日期
* @return String
*/
public Date afterNDay(Date date, int n) {
Calendar c = Calendar.getInstance();
c.setTime(date);
c.add(Calendar.DATE, n);
Date destDay = c.getTime();
return destDay;
}


/**
* 两个日期间的天数
*/
public static int getIntervalDays(Date startday, Date endday) {
if (startday.after(endday)) {
Date cal = startday;
startday = endday;
endday = cal;
}
long sl = startday.getTime();
long el = endday.getTime();
long ei = el - sl;
return (int) (ei / (1000 * 60 * 60 * 24));
}
    
    public static boolean  verifyDate(String birthday){
    String [] array = birthday.split("-");
    if(null == array || array.length != 3 || array[0].length() !=4 || array[1].length() != 2 || array[2].length() != 2) 
    return false;
    int curyear = DateUtil.getYear(new Date());
    try {
int studyear = Integer.parseInt(array[0]);
if(studyear <= 1900 || studyear > curyear)
return false;
String curDateStr = formatDateByFormat(new Date(), DATE_FORMAT);
if(birthday.compareTo(curDateStr) >= 0) 
return false;
return checkDate(birthday);
} catch (NumberFormatException e) {
return false;
}
    }
    
    private static boolean checkDate(String date) {
// System.out.println(date);
// 判断年月日的正则表达式，接受输入格式为2010-12-24，可接受平年闰年的日期
String regex = "(([0-9]{3}[1-9]|[0-9]{2}[1-9][0-9]{1}|[0-9]{1}[1-9][0-9]{2}|[1-9][0-9]{3})-(((0[13578]|1[02])-(0[1-9]|[12][0-9]|3[01]))|((0[469]|11)-(0[1-9]|[12][0-9]|30))|(02-(0[1-9]|[1][0-9]|2[0-8]))))|((([0-9]{2})(0[48]|[2468][048]|[13579][26])|((0[48]|[2468][048]|[3579][26])00))-02-29)";
Pattern pattern = Pattern.compile(regex);
Matcher matcherObj = pattern.matcher(date);
return matcherObj.matches();
}
    
    public static void main(String [] args) {
    //System.out.println(verifyDate("2012-09-27"));
    String test = ",1.1,1.2,1.3,";
System.out.println(test.split(",").length);
    }

}