Help!! writeUTF is writing some junk chars to my file

Question

hi guys,
I am breaking my head with this. please help me out
I wrote a servlet which reads the input sent by an applet
the applet sends a hashmap object called manifest to the servlet
i am reading the contents of this manifest object into a file using writeUTF
but when i open the file to check the contents
every line has some erroneous characters at the beggining of the line
i am not understanding why these junk characters are writted, when i am making sure that i am writing correctly
i am appending the code also to this, please verify:
File lmin = new File(userFile.getPath()+"/"+"Lmin.txt");
FileOutputStream tolmin = new FileOutputStream(lmin);
DataOutputStream dos = new DataOutputStream(tolmin);
out.writeUTF("s&f"+(String)manifest.get("s&f")); //manifest is Hashmap object
dos.writeUTF(manifest.get("-s").toString().trim()+"\n");
when i am printing manifest.get("-s").toString().trim() to the outputstream it doesn't show any additional characters, but the file Lmin.txt has these junk characters.
why is this so??
thanks
pre_pra

Answer 1

I've simplified your code.
import java.io.*;
public class Test {
    public static void main(String[] args) throws Exception {
         DataOutputStream dos = new DataOutputStream (new FileOutputStream (new File ("test.bin")));
         dos.writeUTF ("123456");
         dos.close();
}The output is written to a file named test.bin. I've printed the hex dump of the file.
C>hd test.bin
0000    00 06 61 62 63 64 65 66                            ..abcdefYou can see from the dump that writeUTF writes the length of the string (00 06) and then the bytes, encoded in UTF-8 (just ASCII in my case). The junk that you can see in your file is the length of the string that writeUTF wrote to the output file.