Requisições GET/POST usando JAVA SE

URL url = new URL("http://myhost/api/resource");

HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMode("GET");
conn.connect();

StringBuilder sb = new StringBuilder();

try(BufferedReader br = new BufferedReader(new InputStreamReader(in, conn.getInputStream()))){
  String line = br.readLine();
  while(line != null){
    sb.append(line);
    line = br.readLine();
}
}