经典java小程序

//将字符串日期转换成日期类型
public static Timestamp getTimestamp(String tDate){
 if(tDate!=null){
       Timestamp ts = Timestamp.valueOf(tDate+" 00:00:000000000");
       return ts;
 }
 return null;
}

//得到某年某月有多少天
public static int getLastDayOfMonth(int year,int mon){
 int LastDayOfMonth = 0;
 try{
   Calendar aa = Calendar.getInstance();
   aa.set(year, mon-1, 1);
   aa.roll(Calendar.DATE, -1);
      LastDayOfMonth = aa.get(Calendar.DATE);    
 }catch(Exception e){
  e.printStackTrace();
 }
 return LastDayOfMonth;
}

//去掉字符串首尾的空格
public static String getStringByRegex(String str){
 String reg = "(^\\s*)|(\\s*$)";                             //匹配首尾空格正则模式
 if(str != null){
  str = str.replaceAll(reg, "");
 }
 return str;
}

//对字符串数组进行排序
public static String[] StrArraySort(String[] arr){
 Comparator cmp = (RuleBasedCollator)java.text.Collator.getInstance(java.util.Locale.CHINA);
 java.util.Arrays.sort(arr, cmp);
 return arr;
}

//根据要保留的小数位数dit,将rander四舍五入
public static double getNumberRound(double rander, int dit){
    double iRound;
    BigDecimal bd = new BigDecimal(rander);
    iRound = bd.setScale(dit, BigDecimal.ROUND_HALF_DOWN).doubleValue();
    return iRound;
}

//获取yyyy-MM-dd是星期几
public static int getWeekdayOfDateTime(String datetime){
   DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
   Calendar c = Calendar.getInstance();  
      try {
  c.setTime(df.parse(datetime));
   } catch (Exception e) {
  e.printStackTrace();
   }
   int weekday = c.get(Calendar.DAY_OF_WEEK)-1;
   return weekday;
}

//24小时制的分钟自减器(将HH修改为hh则是12小时制)
public static String getMinByNowDate(String dateTime,int i){
 String dt = "";
 if(dateTime!=null){
   Calendar now = Calendar.getInstance();
   Timestamp ts = Timestamp.valueOf(dateTime);
   now.setTime(ts);
      SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   now.add(Calendar.MINUTE,-(i));
   dt = formatter.format(now.getTime());
 }
 return dt;
}

对于下面的程序, 如果日期格式不一样怎么办? MM/dd/yyyy和dd/MM/yyyy , 它是怎么样分的?

public static Timestamp getTimestamp(String tDate){
if(tDate!=null){
       Timestamp ts = Timestamp.valueOf(tDate+" 00:00:000000000");
       return ts;
}
return null;
}

这些小程序本来就我们项目开发中一个工具类，仅供参考．呵呵．．
另外里面的一些日期转换的方法中的日期格式必须为：yyyy-mm-dd