我要问

Question

package io;import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;/**
 *
 * @author Administrator
 */
public class Bufferedwriter {
    
    /** Creates a new instance of Bufferedwriter */
    public Bufferedwriter() {
    }
    public static void main(String[] args)throws FileNotFoundException, IOException
    {
        FileWriter fw=new FileWriter("a.txt");
        BufferedWriter bw=new BufferedWriter(fw);
        bw.write("aaaaaaa");
        fw.close();
        bw.flush();
    }
}
程序运行时错误
init:
deps-jar:
compile-single:
run-single:
Exception in thread "main" java.io.IOException: Stream closed
        at sun.nio.cs.StreamEncoder.ensureOpen(StreamEncoder.java:38)
        at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:129)
        at java.io.OutputStreamWriter.write(OutputStreamWriter.java:191)
        at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:111)
        at java.io.BufferedWriter.flush(BufferedWriter.java:235)
        at io.Bufferedwriter.main(Bufferedwriter.java:32)
Java Result: 1
生成成功（总时间：0 秒）
是什么意思,为什么文件中的aaaaaaa没有被写进去？？