Python Simple Solution with explanations
\nclass CombinationIterator:\n     \n    def __init__(self, characters: str, combinationLength: int):\n        \n        #using itertools.combinations to genera
```\nclass CombinationIterator:\n     \n    def __init__(self, characters: str, combinationLength: int):\n        \n        #using itertools.combinations to generate all combinations of characters of length combinationLength\n        self.combination = [\'\'.join(combo) for combo in combinations(characters, combinationLength)]\n        \n        #counter to keep track of iterator\'s next\n        self.counter = 0\n        \n        \n    def next(self) -> str:\n        #check if there is a next\n        if self.hasNext():\n            #counter must be updated\n            self.counter += 1\n            \n            return self.combination[self.counter - 1]\n\n    def hasNext(self) -> bool:\n        \n        #check if counter did not reach end\n        return  self.counter < len(self.combination)\n```
['Python3']