Reader in = new InputStreamReader(new FileInputStream("myutf16file.xml"),"UTF-16");
Writer out = new OutputStreamWriter(new FileOutputStream("myutf8file.xml"),"UTF-8");
char[] buffer = new char[1024];
int read;
while((read = in.read(buffer)) != -1){
  out.write(buffer,0,read);
}
in.close();
out.flush();
out.close();