Java多线程环境下SimpleDateFormat类安全转换

Java多线程环境下SimpleDateFormat类安全转换

一、SimpleDateFormat类

package state;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

/**

* SimpleDateFormat类负责日期的转换与格式化

* 解决SimpleDateFormat类多线程环境下转换错误问题

* @author zc

*

*/

public class SimpleDateFormatThread extends Thread{

private SimpleDateFormat sdf;

private String dateString;

public SimpleDateFormatThread(SimpleDateFormat sdf,String dateString) {

super();

this.sdf =sdf;

this.dateString =dateString;

}

@Override

public void run() {

try {

//System.out.println(dateString);

//刚开始日期格式设置错误为YYYY-MM-dd

Date date =DateTools.getSimpleDateFormat("yyyy-MM-dd").parse(dateString);

// System.out.println(date);

String newDateString =DateTools.getSimpleDateFormat("yyyy-MM-dd").format(date).toString();

if(!newDateString.equals(dateString)) {

System.out.println("ThreadName="+this.getName()+"报错日期"+dateString+" 转换日期"+newDateString);

}else {

System.out.println("ThreadName="+this.getName()+"日期"+dateString+" 转换日期"+newDateString);

}

} catch (ParseException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

public static void main(String[] args) {

SimpleDateFormat sdf =new SimpleDateFormat("yyyy-MM-dd");

String[] dateStringArray =new String[]{

"2020-02-05","2020-02-06","2020-02-07","2020-02-08"

};

SimpleDateFormatThread []threadArray= new SimpleDateFormatThread[4];

for(int i=0;i<4;i++) {

threadArray[i] =new SimpleDateFormatThread(sdf,dateStringArray[i]);

}

for(int i=0;i<4;i++) {

threadArray[i].start();

}

}

}

class DateTools{

//ThreadLocal能使线程绑定到指定的对象

private static ThreadLocal t = new ThreadLocal();

public static SimpleDateFormat getSimpleDateFormat(String datePattern) {

SimpleDateFormat sdf=null;

sdf =t.get();

if(sdf==null) {

sdf =new SimpleDateFormat(datePattern);

t.set(sdf);

}

return sdf;

}

}

二、线程状态和线程组

(2)线程5状态

//NEW 尚未启动的线程

//RUNNABLE Java虚拟机中执行的线程

//TERMINATED 已经退出的线程

//BLOCKED 阻塞受监视的线程

//WAITING 无限等待另一个线程

//TIMED_WAITING 等待另一个线程指定时间

package state;

/**

* 线程中状态和线程组

* @author zc

*

*/

public class MyThread extends Thread{

//NEW

//RUNNABLE

//TERMINATED

//BLOCKED

//WAITING

//TIMED_WAITING

public MyThread() {

System.out.println("构造方法中的状态: "+Thread.currentThread().getState());

}

@Override

public void run() {

System.out.println("run方法中的状态:"+Thread.currentThread().getState());

try {

Thread.sleep(1000);

} catch (InterruptedException e) {

// TODO Auto-http://generated catch block

e.printStackTrace();

}

}

public static void main(String[] args) {

MyThhttp://read myThread = new MyThread();

System.out.println("main方法中的状态1 "+ myThread.getState());

Thread t1 = new Thread();

Thread t2 = new Thread();

ThreadGroup group =new ThreadGroup("左氏线程组");

Thread t3 = new Thread(group,t1);

Thread t4 = new Thread(group,t2);

t3.start();

t4.start();

System.out.println("活动的线程数量为: " +group.activeCount());

System.out.println("线程组的名称为: "+group.getName());

try {

myThread.start();

Thread.sleep(1000);

System.out.println("main方法中的状态2 "+ myThread.getState());

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

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