In a jsp I tried:

    String error="";
    boolean success = false;

    try {
   
       
        filename="/home/mydir/temp.txt";
        File myfile = new File(filename);
                            success = myfile.createNewFile();

   
    } catch (IOException e) {
        error= e + "";
    }

I get:

success=false;

error=java.io.IOException: No such file or directory
/home/mydir/temp.txt

Permissions ok