BufferedInputStream does not flush even when the program exits.

Test Program T1.java
----------------
import java.io.*;

class T1 {
    public static void main(String argv[]){
        BufferedOutputStream b;
        String filename;
        String outstr;
 
        filename = "/tmp/b";
        outstr = "Hello";
        try {
            b = new BufferedOutputStream (new FileOutputStream(filename));
            for (int i =0; i<outstr.length(); i++) {
                b.write(outstr.charAt(i));
            }
        } catch (IOException e) {
            System.err.println("Exception");
            System.exit(1);
        }
    }
}


$ javac T1.java
$ java T1
$ cat /tmp/b
$