getting data from servlet to jsp page

It looks like you actual problem is that you want to pass two strings (the book name and the course) in a single AJAX response, but you don't know how to separate them in you JavaScript code.

If so, the answer is to use the .split() method, e.g. like this:

// assumes that the strings are separated by line breaks ("\n")
var lines = xmlhttp.responseText.split("\n");
document.getElementById("tb2").value = lines[0];
document.getElementById("tb3").value = lines[1];

Of course, to make this work, in your Servlet you need to ensure that the two strings are in fact separated by newlines, either by explicitly writing a "\n" between them or by using .writeln(). You also need to make sure that none of the strings themselves can even contain a newline; for your data, that seems likely, but you ought to check it anyway.

If you wish to pass more complicated data back from your Servlet, the standard format for that is JSON. In your Servlet, you can encode your data into JSON using a library like JSON.simple, while in JavaScript, at least in modern browsers, you can use the built-in JSON parser, e.g. like this:

// assumes that the response is JSON, e.g.:
// { book: "English", course: "6th standard" }
var data = JSON.parse( xmlhttp.responseText );
document.getElementById("tb2").value = data.book;
document.getElementById("tb3").value = data.course;

The main advantage of using JSON, besides the ability to transmit more complex data structures, is that if you use a proper JSON library to generate it, you can pass arbitrary strings without having to worry about whether they, say, contain newlines or not.

I would also like to make a few more suggestions. One is not to use XMLHttpRequest directly, but to instead use a library like jQuery that provides a more convenient interface. Using jQuery, your entire client-side code (assuming the server returns JSON) can be simplified to just:

$('#tb1').on( 'keyup', function () {
   $.ajax( {
      url: 'Demo',                 // URL of Servlet
      data: { q: this.value },     // parameters to Servlet
      dataType: 'json',            // type of data to expect back

      success: function ( data ) {
          $('#tb2').val( data.book );
          $('#tb3').val( data.course );
      }
   } );
} );

or, if your server returns plain text with, say, newline separators:

$('#tb1').on( 'keyup', function () {
   $.ajax( {
      url: 'Demo',
      data: { q: this.value },
      dataType: 'text',

      success: function ( text ) {
          var lines = text.split( "\n" );
          $('#tb2').val( lines[0] );
          $('#tb3').val( lines[1] );
      }
   } );
} );

Note that this code directly attaches the keyup handler via jQuery (since that's considered good style), so you don't need the onkeyup="get(this.value)" attribute in your HTML. It also fixes a bunch of bugs in your original code, like the fact that you forgot to URL-encode the q parameter value.

The other suggestion, which I already made on meta.SE, is that you might want to spend some time learning to walk (e.g. how to use .split() and JSON) before trying to run (e.g. writing Servlets to return data via AJAX). For that, a few hours with good introductory tutorial to Java and JavaScript may be more useful than a dozen questions on Stack Overflow.