日期处理工具类 -【一】

1、将一个字符串日期转换成日期格式

/**
 * 将一个字符串日期转换成日期格式
 * @param date
 * @param pattern
 * @return
 */
public static Date toDate(String date, String pattern) {
    if (("" + date).equals("")) {
        return null;
    }
    if (pattern == null) {
        pattern = "yyyy-MM-dd";
    }
    SimpleDateFormat sdf = new SimpleDateFormat(pattern);
    Date newDate = new Date();
    try {
        newDate = sdf.parse(date);
    } catch (Exception ex) {
        ex.printStackTrace();
    }
    return newDate;
}

2、把日期转换成字符串型

/**
 * 把日期转换成字符串型
 * @param date
 * @param pattern
 * @return
 */
public static String toString(Date date, String pattern) {
    if (date == null) {
        return "";
    }
    if (pattern == null) {
        pattern = "yyyy-MM-dd";
    }
    String dateString = "";
    SimpleDateFormat sdf = new SimpleDateFormat(pattern);
    try {
        dateString = sdf.format(date);
    } catch (Exception ex) {
        ex.printStackTrace();
    }
    return dateString;
}

3、计算两个日期之间相差的天数

/** 
 * 计算两个日期之间相差的天数 
 * @param date1 
 * @param date2 
 * @return 
 */  
public static int daysBetween(Date smdate,Date bdate)  {  
    long between_days = 0;
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    try {
        smdate = sdf.parse(sdf.format(smdate));
        bdate = sdf.parse(sdf.format(bdate));
        Calendar cal = Calendar.getInstance();  
        cal.setTime(smdate);  
        long time1 = cal.getTimeInMillis();   
        cal.setTime(bdate);  
        long time2 = cal.getTimeInMillis();       
        between_days=(time2-time1)/(1000*3600*24);           
    } catch (ParseException e) {
        e.printStackTrace();
    }       
    return Integer.parseInt(String.valueOf(between_days));     
}