How can I programmatically test an HTTP connection?

The solution as a unit test:

public void testURL() throws Exception {
    String strUrl = "http://stackoverflow.com/about";

    try {
        URL url = new URL(strUrl);
        HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
        urlConn.connect();

        assertEquals(HttpURLConnection.HTTP_OK, urlConn.getResponseCode());
    } catch (IOException e) {
        System.err.println("Error creating HTTP connection");
        e.printStackTrace();
        throw e;
    }
}

Since java 5 if i recall, the InetAdress class contains a method called isReachable(); so you can use it to make a ping implementation in java. You can also specify a timeout for this method. This is just another alternative to the unit test method posted above, which is probably more efficient.