static classes(when dealing with adapters)

you might normally come across when you call the adapter from another class, they ask the class to be static

eg: private TescoJsonParser TJP= new TescoJsonParser();
String sessionkey= TescoJsonParser.login("youremail@gmail.com","password");
ProductDetails parsedResult=TescoJsonParser.getProductByBarcode(contents,sessionkey );
products.add(parsedResult);
productLists.setAdapter(new ProductViewAdapter(this,products));

I cannot use TJP.login(....,...);
here is why:
http://www.javaworld.com/javaworld/javaqa/1999-08/01-qa-static2.html