Question

I have no idea why, but when I use URLConnection to send a http post request to a url, I can get rhe return fine, but when I use it in an if statement, it stops working.
The program compiles and all that, but if I was to use it to send a http request to a webpage containing yes, and I used the code if(answer.toString == "yes") it would not execute the code inside the if part. I know that it is probably to do with line seperators and such, but could anyone point to me how to fix it.

Code used to get the variable answer:

String data="param1=test1&param2=test2";
try{
  URL lUrl=new URL("http://localhost/test.php");
  URLConnection conn=lUrl.openConnection();
  conn.setDoOutput(true);
  OutputStreamWriter writer=new OutputStreamWriter(conn.getOutputStream());
  writer.write(data);
  writer.flush();
  StringBuffer answer=new StringBuffer();
  BufferedReader reader=new BufferedReader(new InputStreamReader(conn.getInputStream()));
  String line;
  while((line=reader.readLine())!=null){
    answer.append(line);
  }
  writer.close();
  reader.close();
  if(answer.toString()=="yes"){
    System.out.print("1");
  }else{
    System.out.print(answer.toString());
  }
}catch(MalformedURLException ex){
  ex.printStackTrace();
}catch(IOException ex){
  ex.printStackTrace();
}

Answer 1

To compare java strings, use the equals method, not ==.

Because == can only detect if two strings are the same instance, not if they contain the same value.

So your test should be :

if ("yes".equals(answer)) {

Note that I write “yes” as recipient of the equals method because writing answer.equals("yes") would cause a NullPointerException when answer is null.
In this case there is no risk of having answer null but it’s a good habit.