HttpClient httpclient = HttpClientBuilder.create().build();

/* Assemble the login request URL */
String loginURL = LOGINURL +
                  GRANTSERVICE +
                  "&client_id=" + CLIENTID +
                  "&client_secret=" + CLIENTSECRET +
                  "&username=" + USERNAME +
                  "&password=" + PASSWORD;
/* POST Login requests */
HttpPost httpPost = new HttpPost(loginURL);

HttpResponse response = null;
/* Execute the login POST request */
response = httpclient.execute(httpPost);
/* verify response is HTTP OK */
final int statusCode = response.getStatusLine().getStatusCode();
if (statusCode != HttpStatus.SC_OK)
{
    System.out.println("Error authenticating to Force.com: " + statusCode);
    // Error is in EntityUtils.toString(response.getEntity())
    return;
}

HttpResponseProxy {
    HTTP / 1.1 200 OK
    [
        Date : Fri, 21 Oct 2016 10 : 12 : 38 GMT,
        Strict - Transport - Security : max - age = 31536000;
        includeSubDomains,
        Set - Cookie : BrowserId = 3A1ryE8eQa6O - AqbTHyJqQ;
        Path = /;
        Domain=.salesforce.com;Expires=Tue, 20-Dec-2016 10:12:38 GMT,
        Expires: Thu, 01 Jan 1970 00:00:00 GMT,
        Pragma: no-cache,
        Cache-Control: no-cache,
        no-store,
        X-ReadOnlyMode: false,
        Content-Type: application/json;
        charset = UTF - 8,
        Transfer - Encoding : chunked
    ]
    org.apache.http.client.entity.DecompressingEntity @ 892d68
}

HttpResponseProxy {
    HTTP / 1.1 400 Bad Request
    [
        Date : Fri, 21 Oct 2016 10 : 22 : 05 GMT,
        Strict - Transport - Security : max - age = 31536000;
        includeSubDomains,
        Set - Cookie : BrowserId = tbJli6t8SyCbA6I8eA0vow;
        Path = /;
        Domain=.salesforce.com;Expires=Tue, 20-Dec-2016 10:22:05 GMT,
        Expires: Thu, 01 Jan 1970 00:00:00 GMT,
        Pragma: no-cache,
        Cache-Control: no-cache,
        no-store,
        X-ReadOnlyMode: false,
        Content-Type: application/json;
        charset = UTF - 8,
        Transfer - Encoding : chunked
    ]
    ResponseEntityProxy {
        [
            Content - Type : application / json;
            charset = UTF - 8, Chunked : true
        ]
    }
}