Get values for a key in multiple TreeMaps

Dear all,

I have a number of TreeMaps <Long, Integer> each containing values for a specific dataset.

Map<Long, Integer> Heating = new TreeMap<>();
Map <Long, Integer> Cooling = new TreeMap<>();
Map <Long, Integer> Appliances = new TreeMap<>();
etc.

I am now trying to write out the values to a file line by line.  

Usually I iterate through a map in the following way but not sure how to get each value for the same long (Date/TIme) into a string, i.e. Date key , Heating value, Cooling value, Appliances value.

Thanks

Iterator<Map.Entry<Long, Integer>> entries = map.entrySet().iterator();
while (entries.hasNext()) {
    Map.Entry<Long, Integer> entry = entries.next();
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
}

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