XML to JSON

Thanks Mark but i'm not clear how to implement that, with xml the hierarchy was:

xml
tweetElements = xml.getchildElements()
for each tweet in tweetElements


switching json for xml i have:

json
tweetElements =? (what goes here? another "for each"? And for each what of what?
for each tweet in tweetElements'


I changed

 tweetElements = xml.GetChildElements()

to

tweetElements = json

which get me past that point but I'm getting a blank canvas no tweets yet.
I am getting this message in the debugger and cant find what 400 means -

Http: # 5975 done status: 400 

Thanks