【并发编程】ThreadLocal：如何优雅的解决SimpleDateFormat多线程安全问题

package com.ymy.test;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

public class SimpleDateFormatBugTest {

private static SimpleDateFormat sdf = new SimpleDateFormat(“yyyy-MM-dd HH:mm:ss”);

private static Date parse(String date){

Date parse = null;

try {

return sdf.parse(date);

} catch (ParseException e) {

e.printStackTrace();

}

return null;

}

public static void main(String[] args) {

Thread t1 = new Thread(() -> {

Date parse = parse(“2020-12-12 12:12:12”);

System.out.println(“当前日期：” + parse);

});

Thread t2 = new Thread(() -> {

Date parse = parse(“2020-12-12 12:12:12”);

System.out.println(“当前日期：” + parse);

});

Thread t3 = new Thread(() -> {

Date parse = parse(“2018-10-10 10:10:10”);

System.out.println(“当前日期：” + parse);

});

t1.start();

t2.start();

t3.start();

try {

t1.join();

t2.join();

t3.join();

} catch (InterruptedException e) {

e.printStackTrace();

}

System.out.println(“线程执行完毕”);

}

}

执行结果

Exception in thread “Thread-2” Exception in thread “Thread-0” java.lang.NumberFormatException: For input string: “.1102E.1102E22”

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:2089)

at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1869)

at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)

at java.text.DateFormat.parse(DateFormat.java:364)

at com.ymy.test.SimpleDateFormatBugTest.parse(SimpleDateFormatBugTest.java:33)

at com.ymy.test.SimpleDateFormatBugTest.lambda$main$2(SimpleDateFormatBugTest.java:56)

at java.lang.Thread.run(Thread.java:748)

java.lang.NumberFormatException: For input string: “.1102E.1102E22”

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:2089)

at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1869)

at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)

at java.text.DateFormat.parse(DateFormat.java:364)

at com.ymy.test.SimpleDateFormatBugTest.parse(SimpleDateFormatBugTest.java:33)

at com.ymy.test.SimpleDateFormatBugTest.lambda$main$0(SimpleDateFormatBugTest.java:45)

at java.lang.Thread.run(Thread.java:748)

当前日期：Sat Dec 12 12:12:12 CST 2020

线程执行完毕

Process finished with exit code 0

Date日期转String类型（format）

---

package com.ymy.test;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

public class SimpleDateFormatTest {

private static SimpleDateFormat sdf = new SimpleDateFormat(“yyyy-MM-dd HH:mm:ss”);

private static Date d1 = null;

private static Date d2 = null;

private static Date d3 = null;

static {

try {

d1 = sdf.parse(“2020-12-12 12:12