ImperativeStringGroupingLength.java

Map<Integer, List<String>> lengthMap = new HashMap<>();
for(String string : strings)
{
	List<String> sameLength = null;
	Integer length = string.length();
	if(lengthMap.get(length) == null)
	{
		sameLength = new ArrayList<>();
		sameLength.add(string);
		lengthMap.put(length, sameLength);
	}else
	{
		List<String>  sameLengthString = lengthMap.get(length);
		sameLengthString.add(string);
	}

}
return lengthMap;