SimpleDateFormat在多线程如何使用

问题由来

package SimpleDateFormatThread;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Created by Administrator on 2016/11/2.
 */
public class MyThread extends Thread {
    private SimpleDateFormat sdf;
    private String dateString;
    MyThread(SimpleDateFormat sdf, String dateString){
        super();
        this.dateString=dateString;
        this.sdf=sdf;
    }
    public void run(){
        try{
            Date dateRef=sdf.parse(dateString);
            String newDate= sdf.format(dateRef).toString();
            if(!newDate.equals(dateString)){
                System.out.println("Threadneme"+this.getName()+"报错了"+dateString+"转换为"+newDate);
            }
        }catch (ParseException e){
            e.printStackTrace();
        }
    }
}

package SimpleDateFormatThread;

import java.text.SimpleDateFormat;

/**
 * Created by Administrator on 2016/11/2.
 */
public class TestSimpleFormat {
    public static void main(String [] args){
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String [] dateStringArray=new String[]{"2000-01-01","2000-01-02","2000-01-03","2000-01-04",
                "2000-01-05","2000-01-06","2000-01-07","2000-01-08","2000-01-01","2000-01-09","2000-01-10"
        };
        MyThread[] tharray=new MyThread[10];
        for(int i=0;i<10;i++){
            tharray[i]=new MyThread(sdf,dateStringArray[i]);
        }
        for(int i=0;i<10;i++){
            tharray[i].start();
        }
    }
}

结果 是

处理方案之一，每个线程给一个simpledateformat对象

package SimpleDateFormatThread;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Created by Administrator on 2016/11/2.
 */
public class DateTools {
    public static Date parse(String formatpatter,String dateString) throws ParseException {
        return new SimpleDateFormat(formatpatter).parse(dateString);
    }
    public static String format(String formatpatte,Date date){
        return new SimpleDateFormat(formatpatte).format(date).toString();
    }
}

package SimpleDateFormatThread;

import java.text.SimpleDateFormat;

/**
 * Created by Administrator on 2016/11/2.
 */
public class Test1 {
    public static void main(String [] args){
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String [] dateStringArray=new String[]{"2000-01-01","2000-01-02","2000-01-03","2000-01-04",
                "2000-01-05","2000-01-06","2000-01-07","2000-01-08","2000-01-01","2000-01-09","2000-01-10"
        };
        MyThread2[] tharray=new MyThread2[10];
        for(int i=0;i<10;i++){
            tharray[i]=new MyThread2(sdf,dateStringArray[i]);
        }
        for(int i=0;i<10;i++){
            tharray[i].start();
        }
    }
}

结果

结果达到要求 出现原因创建了多个simpledateformat对象

还有一种就是用ThreadLocal类可以使线程绑定到制定对象，修改之 注意 只是可以简化代码而已  ，底层为每个线程new了一个对应的对象

package SimpleDateFormatThread;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Created by Administrator on 2016/11/2.
 */
public class DateToolsa {
    private static ThreadLocal<SimpleDateFormat> t1=new ThreadLocal<SimpleDateFormat>();
   public static SimpleDateFormat getSimpledateformat(String datepatter){
       SimpleDateFormat sdf=null;
       sdf=t1.get();
       if(sdf==null){
           sdf=new SimpleDateFormat(datepatter);
           t1.set(sdf);
       }
       return sdf;
   }
}

package SimpleDateFormatThread;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Created by Administrator on 2016/11/2.
 */
public class MyThread2 extends Thread {
    private SimpleDateFormat sdf;
    private String dateString;
    MyThread2(SimpleDateFormat sdf, String dateString){
        super();
        this.dateString=dateString;
        this.sdf=sdf;
    }
    public void run(){
        try{
            Date dateRef=DateToolsa.getSimpledateformat("yyyy-MM-dd").parse(dateString);
            String newDate= DateToolsa.getSimpledateformat("yyyy-MM-dd").format(dateRef).toString();
            if(!newDate.equals(dateString)){
                System.out.println("Threadneme"+this.getName()+"报错了"+dateString+"转换为"+newDate);
            }
        }catch (ParseException e){
            e.printStackTrace();
        }
    }
}

测试结果