How to avoid a lot of if else conditions

I have read a lot of topics about code refactoring and avoiding of if else statements. Actually, I have a class where I am using a lot of if - else conditions.

More details: I am using the pull parser and on each line of my soap response, I will check if there is a tag I am interested on, if not, check another tag etc:

 if(eventType == XmlPullParser.START_TAG) {
            soapResponse= xpp.getName().toString();
            
            if (soapResponse.equals("EditorialOffice")){  
                eventType = xpp.next();
                if (xpp.getText()!=null){
                editorialOffice += xpp.getText();
                }
            }   
            else if (soapResponse.equals("EditorialBoard")){  
                eventType = xpp.next();
                if (xpp.getText()!=null){
                editorialBoard += xpp.getText();
                }
            }
            else if (soapResponse.equals("AdvisoryBoard")){  
                eventType = xpp.next();
                if (xpp.getText()!=null){
                advisoryBoard += xpp.getText();
                }
            }   
        }
        eventType = xpp.next();
     }

Now, I would like to use something else, instead of those if else conditions, but I don't know what.

Can you please give me an example?

Solution 1:

Try to look at the strategy pattern.

• Make an interface class for handling the responses (IMyResponse)
  • Use this IMyResponse to create AdvisoryBoardResponse, EditorialBoardResponse classes
• Create an dictionary with the soapresponse value as key and your strategy as value
• Then you can use the methods of the IMyResponse class by getting it from the dictionary

Little Example:

// Interface
public interface IResponseHandler {
   public void handleResponse(XmlPullParser xxp);

}

// Concrete class for EditorialOffice response
private class EditorialOfficeHandler implements IResponseHandler {
   public void handleResponse(XmlPullParser xxp) {
       // Do something to handle Editorial Office response
   }
}

// Concrete class for EditorialBoard response
private class EditorialBoardHandler implements IResponseHandler {
   public void handleResponse(XmlPullParser xxp) {
       // Do something to handle Editorial Board response
   }
}

On a place you need to create the handlers:

Map<String, IResponseHandler> strategyHandlers = new HashMap<String,IResponseHandler>();
strategyHandlers.put("EditorialOffice", new EditorialOfficeHandler());
strategyHandlers.put("EditorialBoard", new EditorialBoardHandler());

Where you received the response:

IResponseHandler responseHandler = strategyHandlers.get(soapResponse);
responseHandler.handleResponse(xxp);

Solution 2:

In this particular case, since the code is essentially identical for all 3 case except for the String being appended to, I would have a map entry for each of the Strings being built:

Map<String,String> map = new HashMap<String,String>();
map.put("EditorialOffice","");
map.put("EditorialBoard","");
map.put("AdvisoryBoard","");
// could make constants for above Strings, or even an enum

and then change your code to the following

if(eventType == XmlPullParser.START_TAG) {
    soapResponse= xpp.getName().toString();
    String current = map.get(soapResponse);
    if (current != null && xpp.getText()!=null) {
        map.put( soapResponse, current += xpp.getText());
    }
    eventType = xpp.next();
}

No "if... then... else". Not even the added complexity of multiple classes for strategy patterns, etc. Maps are your friend. Strategy is great in some situations, but this one is simple enough to be solved without.

Solution 3:

In Java 7 you can SWITCH on Strings. You could use that if you could use that ;-)

Solution 4:

Besides zzzzzzz(etc.)'s comment... keep in mind that you are using XmlPullParser which makes you write ugly code like the one you have. You could register some callbacks that would split your code and make it 'better', but if possible, just use SimpleXML library or similar.

Also, you can refactor your code to make it more readable and less verbose. For instance, why do you call xpp.next() inside each if statement? Why not just calling it outside just once:

if(eventType == XmlPullParser.START_TAG) {
    soapResponse= xpp.getName().toString();
    if (soapResponse.equals("EditorialOffice") && xpp.getText()!=null){  
        editorialOffice += xpp.getText();
    }   
    else if (soapResponse.equals("EditorialBoard") && xpp.getText()!=null){  
        editorialBoard += xpp.getText();
    }
    else if (soapResponse.equals("AdvisoryBoard") && xpp.getText()!=null){  
        advisoryBoard += xpp.getText();
    }   
}
eventType = xpp.next();