字符串与 java.sql.Timestamp转换

package com.test;
import java.sql.Timestamp;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateUtil {

private static final String DEFAULT_FORMAT = "yyyy-MM-dd HH:mm:ss.SSS";
private static final String DEFAULT_FORMAT1 = "yyyy-MM-dd HH:mm:ss";
private static final String DEFAULT_FORMAT2 = "yyyy-MM-dd HH:mm";

private DateUtil() {}

public static Date str2Date(String str, String format){
  if (null != str && !"".equals(str)) {
    SimpleDateFormat sdf = new SimpleDateFormat(format);
    Date date = null;
    try {
     date = sdf.parse(str);
     return date;
   } catch (ParseException e) {
     e.printStackTrace();
  }
}
return null;
}

public static String date2Str(Date date, String format) {
  if (null != date && !"".equals(date)) {
    SimpleDateFormat sdf = new SimpleDateFormat(format);
    return sdf.format(date);
  }
  return null;
}

public static String timestamp2Str(Timestamp time) {
  if(null != time && !"".equals(time)){
    Date date = new Date(time.getTime());
    return date2Str(date, DEFAULT_FORMAT);
  }
  return null;
}

public static Timestamp str2Timestamp(String str) {
  if(null != str && !"".equals(str)){
    Date date = str2Date(str, DEFAULT_FORMAT);
    return new Timestamp(date.getTime());
  }
  return null;
}
public static void main(String[] args) throws Exception {
  String tm = "2011-01-01 10:00:00.123";
  Timestamp tstamp = str2Timestamp(tm);
  System.out.println(tstamp);
  System.out.println(timestamp2Str(tstamp));
  System.out.println(timestamp2Str(null));
  System.out.println(str2Timestamp(null));
  }
}