input string to form url to read a file from a server

I have been trying to write an applet which allows the user to input 4 digits and take the input string to form a url
with it.
         I have an applet which can get a file from the server and one which can echo user input but I am stuck.
     
        The url is http://abcdefg/hijkl/m_nnnn.txt 
The user is to input "nnnn" and my applet is supposed to
form the url and display the file in their browser.
I have tried to combime these two programs but the  getfile
program is not quite right because it depends upon having an url in the applettag
The textfield program merely echos the user input.
I want to take that input and then form the url to read the file. Can anyone please help me. Thank you. Joseph Ruisi
        the code to echo user input is -
import java.awt.*;

public class TextFieldTest extends java.applet.Applet {

public void init() {
   
       MyTextField text = new MyTextField();
     add(text);
    }
 }
  class MyTextField extends TextField {
   
       public MyTextField() {
   super("Type Your Text",20);
}
}
and the program to get the file is

import java.awt.*;
import java.net.*;
import java.io.*;


public class getFile extends java.applet.Applet {

TextArea text;
String URLString;

public void init() {
URLString = getParameter("url");
setLayout(new BorderLayout());
}

public void start() {
text = new TextArea();

add("Center",text);
add("South", new Button("press"));
try {
int nread;
byte buffer[] = new byte[1024];
URL url = new URL(URLString);
InputStream is = url.openStream();
while ((nread = is.read (buffer)) > 0) {
text.appendText(new String(buffer, 0));
}
}
catch (Exception exp) {
text.setText("Cannot Load: " + URLString  + "\n" + exp.toString());
}
}

}