public class TestSimpleDateFormat { private static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); public static Date parse(String date) throws ParseException { return DATE_FORMAT.parse(date); } public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newFixedThreadPool(500); for (int i = 0; i < 500; i++) { executorService.execute(new Runnable() { @Override public void run() { for (int i = 0; i < 1000000; i++) { try { DATE_FORMAT.parse("2014-01-01 00:00:00"); } catch (ParseException e) { e.printStackTrace(); } } } }); } Thread.sleep(3000000); } }
报错 Exception in thread ：java.lang.NumberFormatException: For input string: ""
参考:https://www.cnblogs.com/zuoxiaolong/p/con1.html
https://blog.csdn.net/Mrs_chens/article/details/90166399
分析
翻译过来就是：日期格式化的类是非同步的，建议为每一个线程创建独立的格式化实例。如果多个线程并发访问同一个格式化实例，就必须在外部添加同步机制。
解决办法一 加入synchronized 关键字 但是控制台 还会隐约有报错的信息闪过
public class TestSimpleDateFormat { private static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); public static Date parse(String strDate) throws ParseException { synchronized (DATE_FORMAT) { return DATE_FORMAT.parse(strDate); } } public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newFixedThreadPool(500); for (int i = 0; i < 500; i++) { executorService.execute(new Runnable() { @Override public void run() { for (int i = 0; i < 1000000; i++) { try { System.out.println(DATE_FORMAT.parse("2019-05-13 11:30:59")); } catch (ParseException e) { e.printStackTrace(); } } } }); } Thread.sleep(3000000); } }
解决办法二 使用java8 DateTimeFormatter (推荐使用)
public class TestSimpleDateFormat { private static final DateTimeFormatter sdf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"); public static LocalDateTime parse2(String dateNow) { return LocalDateTime.parse(dateNow, sdf); } public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newFixedThreadPool(500); for (int i = 0; i < 500; i++) { executorService.execute(new Runnable() { @Override public void run() { for (int i = 0; i < 1000000; i++) { System.out.println(sdf.parse("2019-05-13 11:30:59")); } } }); } Thread.sleep(3000000); } }
使用 SimpleDateFormat 报错 Exception in thread ：java.lang.NumberFormatException: For input string: ""
原文：https://www.cnblogs.com/wf-zhang/p/12133728.html