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使用 SimpleDateFormat 报错 Exception in thread ：java.lang.NumberFormatException: For input string: "" 

public class TestSimpleDateFormat {

</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> DateFormat DATE_FORMAT = <span style="color: rgba(0, 0, 255, 1)">new</span> SimpleDateFormat("yyyy-MM-dd HH🇲🇲ss"<span style="color: rgba(0, 0, 0, 1)">);

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> Date parse(String date) <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> ParseException {
    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> DATE_FORMAT.parse(date);
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span> main(String[] args) <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> InterruptedException {
    ExecutorService executorService </span>= Executors.newFixedThreadPool(500<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = 0; i &lt; 500; i++<span style="color: rgba(0, 0, 0, 1)">) {
        executorService.execute(</span><span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Runnable() {
            @Override
            </span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> run() {
                </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = 0; i &lt; 1000000; i++<span style="color: rgba(0, 0, 0, 1)">) {
                    </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
                        DATE_FORMAT.parse(</span>"2014-01-01 00:00:00"<span style="color: rgba(0, 0, 0, 1)">);
                    } </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (ParseException e) {
                        e.printStackTrace();
                    }
                }
            }
        });
    }
    Thread.sleep(</span>3000000<span style="color: rgba(0, 0, 0, 1)">);
}



}

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 {

</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> DateFormat DATE_FORMAT = <span style="color: rgba(0, 0, 255, 1)">new</span> SimpleDateFormat("yyyy-MM-dd HH🇲🇲ss"<span style="color: rgba(0, 0, 0, 1)">);

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> Date parse(String strDate) <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> ParseException {

    </span><span style="color: rgba(0, 0, 255, 1)">synchronized</span><span style="color: rgba(0, 0, 0, 1)"> (DATE_FORMAT) {

        </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> DATE_FORMAT.parse(strDate);

    }
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span> main(String[] args) <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> InterruptedException {
    ExecutorService executorService </span>= Executors.newFixedThreadPool(500<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = 0; i &lt; 500; i++<span style="color: rgba(0, 0, 0, 1)">) {
        executorService.execute(</span><span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Runnable() {
            @Override
            </span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> run() {
                </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = 0; i &lt; 1000000; i++<span style="color: rgba(0, 0, 0, 1)">) {
                    </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
                        System.out.println(DATE_FORMAT.parse(</span>"2019-05-13 11:30:59"<span style="color: rgba(0, 0, 0, 1)">));
                    } </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (ParseException e) {
                        e.printStackTrace();
                    }
                }
            }
        });
    }
    Thread.sleep(</span>3000000<span style="color: rgba(0, 0, 0, 1)">);
}



}

 

解决办法二      使用 java8  DateTimeFormatter (推荐使用)

public class TestSimpleDateFormat {

</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> DateTimeFormatter sdf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH🇲🇲ss"<span style="color: rgba(0, 0, 0, 1)">);

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> LocalDateTime parse2(String dateNow) {

    </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> LocalDateTime.parse(dateNow, sdf);

}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span> main(String[] args) <span style="color: rgba(0, 0, 255, 1)">throws</span><span style="color: rgba(0, 0, 0, 1)"> InterruptedException {
    ExecutorService executorService </span>= Executors.newFixedThreadPool(500<span style="color: rgba(0, 0, 0, 1)">);
    </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = 0; i &lt; 500; i++<span style="color: rgba(0, 0, 0, 1)">) {
        executorService.execute(</span><span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> Runnable() {
            @Override
            </span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> run() {
                </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = 0; i &lt; 1000000; i++<span style="color: rgba(0, 0, 0, 1)">) {
                    System.out.println(sdf.parse(</span>"2019-05-13 11:30:59"<span style="color: rgba(0, 0, 0, 1)">));
                }
            }
        });
    }
    Thread.sleep(</span>3000000<span style="color: rgba(0, 0, 0, 1)">);
}



}