解决SimpleDateFormat线程安全问题

 package com.tanlu.user.util;

 import java.text.DateFormat;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.Date;

 /**
  * 考虑到SimpleDateFormat为线程不安全对象，故应用ThreadLocal来解决，
  * 使SimpleDateFormat从独享变量变成单个线程变量
  */
 public class ThreadLocalDateUtil {

     //写法1：
     /*private static ThreadLocal<DateFormat> threadLocal = new ThreadLocal<DateFormat>() {
         @Override
         protected DateFormat initialValue() {
             return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
         }
     };

     public static Date parse(String dateStr) throws ParseException {
         return threadLocal.get().parse(dateStr);
     }

     public static String format(Date date) {
         return threadLocal.get().format(date);
     }*/

     //写法2：
     private static final String date_format = "yyyy-MM-dd HH:mm:ss";
     private static ThreadLocal<DateFormat> threadLocal = new ThreadLocal<DateFormat>();

     public static DateFormat getDateFormat() {
         DateFormat df = threadLocal.get();
         if(df == null){
             df = new SimpleDateFormat(date_format);
             threadLocal.set(df);
         }
         return df;
     }

     public static String formatDate(Date date) throws ParseException {
         return getDateFormat().format(date);
     }

     public static Date parse(String strDate) throws ParseException {
         return getDateFormat().parse(strDate);
     }

 }