Exception: ioexception:stream closed

Abnormal prompt
  Exception in thread “main” java.io.IOException: Stream Closed
   The stream is shut down .
The code is as follows
   It's written that one or more are cut MP3 Merge the files into one MP3 file .

public class MergeFileDemo{
    
	public static void main(String[] args) throws IOException {
    
		File dir=new File("gril");
		mergeFile(dir);
	}

	public static void mergeFile(File dir) throws IOException {
    
		//
		ArrayList<FileInputStream> al=new ArrayList<FileInputStream>();
		for (int i = 1; i <= 5; i++) {
    
			al.add(new FileInputStream(new File(dir,i+".part")));
			Enumeration<FileInputStream> en=Collections.enumeration(al);
			SequenceInputStream sis=new SequenceInputStream(en);
			FileOutputStream fos=new FileOutputStream(new File(dir," Beggars' sect theme .mp3"));
			byte[] buf=new byte[1024];
			int  len=0;
			while((len=sis.read(buf))!=-1) {
    
				fos.write(buf,0,len);
			}
		fos.close();
		sis.close();
		}
	}
}

Problem analysis

   The flow must be closed fos.close(); and sis.close(); Something went wrong. , After careful inspection, it is found that the closed stream is written in for Inside the loop , The flow is turned off at the first cycle . And this for Add all files when looping al.add(); It's over , The following code is also written here , So it caused an exception .

resolvent

	fos.close();
	sis.close();

   Write the flow closure in for Outside of the loop . take for The cyclic code block is modified to the following , Also is to } Put it in al.add(); Back .

	for (int i = 1; i <= 5; i++) {
		al.add(new FileInputStream(new File(dir,i+".part")));
	}