java Long类型转为String类型的两种方式及区别说明

Date date=new Date();
System.out.println(date.getTime());

long mseconds=date.getTime()/1000;

SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  
            java.util.Date date = new Date(mseconds * 1000);  
            String str = sdf.format(date);  
            System.out.println(str);

String str="2015-08-31 21:08:06";
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Date date = (Date) sdf.parse(str);
            System.out.println(date.getTime());

String str="Wed Sep 16 11:26:23 CST 2009";
    SimpleDateFormat sdf = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy", Locale.US);
    Date date = (Date) sdf.parse(str);

import java.text.*;
import java.util.*;
public class DateFormat {
    /**
     * date类型进行格式化输出
     * @param date
     * @return
     */
    public static String dateFormat(Date date) {
          SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
          String dateString = formatter.format(date);
          return dateString;
     }
    /**
     * 将"2017-08-9 21:08:06"型字符串转化为Date
     * @param str
     * @return
     * @throws ParseException
     */
    public static Date StringToDate(String str) throws ParseException{
        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date date = (Date) formatter.parse(str);
        return date;
    }
    /**
     * 将CST时间类型字符串进行格式化输出
     * @param str
     * @return
     * @throws ParseException
     */
    public static String CSTFormat(String str) throws ParseException{
            SimpleDateFormat formatter = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy", Locale.US);
            Date date = (Date) formatter.parse(str);
            return dateFormat(date);
    }
    /**
     * 将long类型转化为Date
     * @param str
     * @return
     * @throws ParseException
     */
    public static Date LongToDare(long str) throws ParseException{      
        return new Date(str * 1000);  
    }
}