How to count repeated words number in a Sentence

Lets have a sentence 'That that exists exists in that that that that exists exists in' and we need to find the occurence of top words. So just we pass the string in the below

method and we can get the occurence of words.

 def getTopWord(String sentence){
		List keywords = sentence.split("\\s+") // whitespace regex
		List resultData = new ArrayList()
		Map topwords = new HashMap()
		keywords.each{String word->
			if(topwords.containsKey(word.toLowerCase())){
				topwords.put(word.toLowerCase(), topwords.get(word.toLowerCase()) + 1)
			}else{
				topwords.put(word.toLowerCase(),1)
			}
		}
		Map sortedMap = topwords.sort { a, b -> b.value <=> a.value } // for sorting by top occurence
		sortedMap.each{key, value ->
			Map data = new HashMap()
			data.word = key
			data.occurence = value
			resultData.add(data)
		}
		log.debug'All Data  '+resultData
	}

The output will be as [[occurence:6,word:that], [occurence:4,word:exists], [occurence:2,word:in]]