This is an extension of my earlier question where i was using normalizeSpace(). But since this available only from api 26. How do we remove the whitespaces for earlier versions
If going back to basics I would suggest using the trim() function followed by a regex replacement using replaceAll() that matches instances of the space characters i.e.
(\\s+) and replaces them with a single space.
String str = ' how is the weather today '; str = str.trim(); str = str.replaceAll('(\\s+)', ' '); return str;