Как отправить get http запрос?

Например, так

String url = "http://www.google.com/";

URL urlobj = new URL(url);
HttpURLConnection connection = (HttpURLConnection) urlobj.openConnection();

connection.setRequestMethod("GET");

BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream())); 
String inputLine; 
StringBuffer response = new StringBuffer();

while ((inputLine = in.readLine()) != null) {
    response.append(inputLine); 
} 
in.close();

System.out.println(response.toString());

Или например вот так.

dependencies {
implementation 'com.loopj.android:android-async-http:1.4.5'
}

String result будет содержать результат запроса.

    String URL = "http://www.google.com/";

    AsyncHttpClient client = new AsyncHttpClient();
    client.get(URL, new AsyncHttpResponseHandler() {
    @Override
    public void onSuccess(int statusCode, Header[] headers, byte[] responseBody) {
        String result = new String (responseBody);
    }

    @Override
    public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable error) {

    }
})