Trigger dropdown menus above elements by adding .dropup to the parent.
<!DOCTYPE HTML>
<html>
<head>
<link href="http://java2s.com/style/bootstrap.min.css" rel="stylesheet">
<script src="http://java2s.com/style/jquery-1.8.0.min.js"></script>
<script src="http://java2s.com/style/bootstrap.min.js"></script>
</head><!--from www .j a v a 2 s .c o m-->
<body style='margin: 20px;'>
<div class="btn-toolbar">
<div class="btn-group dropup">
<button type="button" class="btn btn-default">Dropup</button>
<button type="button" class="btn btn-default dropdown-toggle"
data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu">
<li><a href="#">Action</a></li>
<li><a href="#">Another action</a></li>
<li><a href="#">Something else here</a></li>
<li class="divider"></li>
<li><a href="#">Separated link</a></li>
</ul>
</div>
<!-- /btn-group -->
<div class="btn-group dropup">
<button type="button" class="btn btn-primary">Right dropup</button>
<button type="button" class="btn btn-primary dropdown-toggle"
data-toggle="dropdown">
<span class="caret"></span>
</button>
<ul class="dropdown-menu pull-right">
<li><a href="#">Action</a></li>
<li><a href="#">Another action</a></li>
<li><a href="#">Something else here</a></li>
<li class="divider"></li>
<li><a href="#">Separated link</a></li>
</ul>
</div>
<!-- /btn-group -->
</div>
</body>
</html>