求助。多線程讀取文件相互影響

for(.......) {

new Thread(new Runnable(){

@Override

public void run() {

//讀取文件

ReadUtil.read();

}

}).start();

}

//-----------讀取文件的操做------------

public synchronized static read() {

File file=new File("F://info/訂單信息.xls");  

        Workbook wb=null;  

        try {  

            //傳入的是文件,獲取工做薄 

        wb = Workbook.getWorkbook(file); 

       

            if(wb!=null){  

//do .......

            }  

        } catch (BiffException e) {  

            e.printStackTrace();  

        } catch (IOException e) {  

            e.printStackTrace();  

        }finally {    

            wb.close();    

        }

}

若是這個方法不加「同步」的話，就會報錯。空指針異常是wb.close()這塊。

我不理解的是我啓動了多個線程，應該就有多個實例ReadUtils之間的讀取文件應該互不干擾纔對，爲何一個線程會把另外一個線程的IO流給關了。。。

後臺錯誤信息以下：

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