求助。多线程读取文件相互影响

for(.......) {

new Thread(new Runnable(){

@Override

public void run() {

//读取文件

ReadUtil.read();

}

}).start();

}

 

//-----------读取文件的操作------------

public synchronized static read() {

File file=new File("F://info/订单信息.xls");  

        Workbook wb=null;  

        try {  

            //传入的是文件,获取工作薄 

        wb = Workbook.getWorkbook(file); 

        

            if(wb!=null){  

//do .......

            }  

        } catch (BiffException e) {  

            e.printStackTrace();  

        } catch (IOException e) {  

            e.printStackTrace();  

        }finally {    

            wb.close();    

        }

}

 

如果这个方法不加“同步”的话，就会报错。空指针异常是wb.close()这块。

我不理解的是我启动了多个线程，应该就有多个实例ReadUtils之间的读取文件应该互不干扰才对，为什么一个线程会把另一个线程的IO流给关了。。。

后台错误信息如下：

Exception in thread "Thread-1" java.lang.NullPointerException

at com.excle.jxl4mysql.ReadUtil.read(ReadUtil.java:122)

at com.excle.jxl4mysql.ReadThread$1.run(ReadThread.java:36)

at java.lang.Thread.run(Thread.java:619)

Exception in thread "Thread-2" java.lang.NullPointerException

at com.excle.jxl4mysql.ReadUtil.read(ReadUtil.java:122)

at com.excle.jxl4mysql.ReadThread$1.run(ReadThread.java:36)

at java.lang.Thread.run(Thread.java:619)

Exception in thread "Thread-5" java.lang.NullPointerException

at com.excle.jxl4mysql.ReadUtil.read(ReadUtil.java:122)

at com.excle.jxl4mysql.ReadThread$1.run(ReadThread.java:36)

at java.lang.Thread.run(Thread.java:619)

Exception in thread "Thread-8" java.lang.NullPointerException

at com.excle.jxl4mysql.ReadUtil.read(ReadUtil.java:122)

at com.excle.jxl4mysql.ReadThread$1.run(ReadThread.java:36)

at java.lang.Thread.run(Thread.java:619)

Exception in thread "Thread-7" java.lang.OutOfMemoryError: Java heap space

Exception in thread "Thread-6" java.lang.OutOfMemoryError: Java heap space

Exception in thread "Thread-3" java.lang.OutOfMemoryError: Java heap space