Look at the wired error!

Question

Look at the following code(about XML parsing but it does not matter with the error):
Element header = (Element) document.createElement("WfMessageHeader");
if (msg.isResponse)
Element requestOrResponse = (Element) document.createElement("Response");
else
Element requestOrResponse = (Element) document.createElement("Request");
requestOrResponse.setAttribute ("ResponseRequired", "Yes");
Random r = new Random();
int senderId = r.nextInt(1000);
String keyStr = "www.sender.com/id".concat((new Integer(senderId)).toString());
Element key = (Element) document.createElement("Key");
key.appendChild( document.createTextNode(keyStr) );
header.appendChild(requestOrResponse);
The compiling said:
.\messager\CommModel.java:433: cannot resolve symbol
symbol : variable requestOrResponse
location: class messager.CommModel
header.appendChild(requestOrResponse);
^
Why? Thanks.

Answer 1

Because requestOrResponse is declared within if { .. } and else { .. }, it may only be accessed within those blocks.
Instead, you can do:
Element requestOrResponse = null;
if {
  requestOrResponse = ...;
else {
  requestOrResponse = ...;
}