Edit in JSFiddle

(function ($) {
    $('#add_multiple').on('click', function () {
        var multiple_text_to_add = $('#multiple_add_text').val();
        if ($.trim(multiple_text_to_add) == "") return;

        var multiple_text_to_add_array = multiple_text_to_add.split(",");

        $(multiple_text_to_add_array).each(function (k, v) {
            $('#languages2').append(
                "<option value='" + v + "'>" + v + "</option>");
        });

    });
})(jQuery);

<br/>
<input type="text" id="multiple_add_text" placeholder="JAVA,C#" class="form-control">(comma separated)
<input type="button" value="Add" class="btn btn-primary " id="add_multiple">
<div class="code_example">
    <select name="languages" id="languages2">
        <option value="c">C</option>
        <option value="c++">C++</option>
        <option value="php">PHP</option>
        <option value="perl">PERL</option>
        <option value="ruby">RUBY</option>
        <option value="python">PYTHON</option>
        <option value="go">GO</option>
    </select>
</div>