SimpleDateFormat--线程安全的操作方法(有实例)

迈不过友情╰ 2023-10-02 13:05 5阅读 0赞

原文网址：[SimpleDateFormat--线程安全的操作方法(有实例)\_IT利刃出鞘的博客-CSDN博客][SimpleDateFormat--_IT_-CSDN]

## 简介 ##

本文用示例介绍Java中的SimpleDateFormat的线程安全的操作方法，也介绍SimpleDateFormat为什么不是线程安全的。这两个问题也是面试中常见的问题。

## 线程不安全实例 ##

package org.example.a;
    
    import java.text.DateFormat;
    import java.text.SimpleDateFormat;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    import java.util.concurrent.*;
    
    public class Demo{
        public static void main(String[] args) {
            final DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Callable<Date> task = new Callable<Date>() {
                public Date call() throws Exception {
                    return dateFormat.parse("2016-12-18 15:00:34");
                }
            };
    
            // 创建5个线程的线程池
            ExecutorService exec = Executors.newFixedThreadPool(5);
            List<Future<Date>> results = new ArrayList<Future<Date>>();
            for (int i = 0; i < 10; i++) {
                results.add(exec.submit(task));
            }
            exec.shutdown();
            // 输出结果
            for (Future<Date> result : results) {
                try {
                    System.out.println(result.get());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                }
            }
        }
    }

执行结果（出现异常）

Sun Dec 18 15:00:34 CST 2016
    Sun Dec 18 15:00:34 CST 2016
    Sun Dec 18 15:00:34 CST 2016
    java.util.concurrent.ExecutionException: java.lang.NumberFormatException: For input string: "E34"
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:192)
        at org.example.a.Demo.main(Demo.java:29)
    Caused by: java.lang.NumberFormatException: For input string: "E34"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
        at java.lang.Long.parseLong(Long.java:589)
        at java.lang.Long.parseLong(Long.java:631)
        at java.text.DigitList.getLong(DigitList.java:195)
        at java.text.DecimalFormat.parse(DecimalFormat.java:2051)
        at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:2162)
        at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
        at java.text.DateFormat.parse(DateFormat.java:364)
        at org.example.a.Demo$1.call(Demo.java:15)
        at org.example.a.Demo$1.call(Demo.java:13)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
    java.util.concurrent.ExecutionException: java.lang.NumberFormatException: For input string: "E342"
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    Sun Dec 18 15:00:34 CST 2016    at org.example.a.Demo.main(Demo.java:29)
    Caused by: java.lang.NumberFormatException: For input string: "E342"
        at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
        at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
        at java.lang.Double.parseDouble(Double.java:538)
        at java.text.DigitList.getDouble(DigitList.java:169)
        at java.text.DecimalFormat.parse(DecimalFormat.java:2056)
        at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:2162)
        at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
        at java.text.DateFormat.parse(DateFormat.java:364)
        at org.example.a.Demo$1.call(Demo.java:15)
        at org.example.a.Demo$1.call(Demo.java:13)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
    
    java.util.concurrent.ExecutionException: java.lang.NumberFormatException: For input string: ""
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:192)
        at org.example.a.Demo.main(Demo.java:29)
    Caused by: java.lang.NumberFormatException: For input string: ""
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
        at java.lang.Long.parseLong(Long.java:601)
        at java.lang.Long.parseLong(Long.java:631)
        at java.text.DigitList.getLong(DigitList.java:195)
        at java.text.DecimalFormat.parse(DecimalFormat.java:2051)
        at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:2162)
        at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
        at java.text.DateFormat.parse(DateFormat.java:364)
        at org.example.a.Demo$1.call(Demo.java:15)
        at org.example.a.Demo$1.call(Demo.java:13)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
    Sun Dec 18 15:00:34 CST 2016
    Sun Dec 18 15:00:34 CST 2016
    Sun Dec 18 15:00:34 CST 2016

## 线程不安全原因 ##

上边是文章的部分内容，为便于维护，全文已迁移到此网址：[SimpleDateFormat-线程安全的操作方法(有实例) - 自学精灵][SimpleDateFormat-_ -]

[SimpleDateFormat--_IT_-CSDN]: https://knife.blog.csdn.net/article/details/121004863
[SimpleDateFormat-_ -]: https://learn.skyofit.com/archives/353