Data Structure for an array of Dictionary entries

Question

I am looking for a native way (preferably) in java to implement a data structure to hold an int as key and a set of key/value pair as the value. In essence if would be an array of dictionaires referenced by an index.

Ex:

MyDataStructure[[Key,Value]] foo = new ...

foo.put[["hello", "world"], ["so","rocks"]]

println(foo[0].getValue("hello")) would print out "world" and println(foo[0].getValue("so")) would print out "rocks"

Answer 1

• If you know in advance number of dictionaries, then minimum structure is array of Map:

  Map<Key,Value>[] dictonaires = new HashMap<Key,Value>[20];
  for (int i=0; i<dictionaries.length; i++) {
      dictionaries[i] = new Hashmap<Key,Value>();
  }
  
  // Any time later, refer to a dictionary by index 
  Map<Key,Value> currentDictionary = dictionaries[10];
  // Can call currentDictionar.put/get/remove to create or update/read/delete 
  // entries, but can't add/remove entire dictionaries
  

• But a more flexible structure is List<Map<Key,Value>>, because number of dictionaries can change dynamically. Any List will work - but in your case, ArrayList would be best for fast access (get) by index:

  List<Map<Key,Value>> dictionaryList = new ArrayList<Map<Key,Value>>();
  
  // Then add new dictionary anytime later:
  dictionaryList.add(new HashMap<Key,Value>());    
  
  // Access by index (index matches order of adding):
  Map<Key,Value> currentDictionary = dictionaryList.get(10);    
  // Can call currentDictionar.put/get/remove to create or update/read/delete 
  // entries, but can't add/remove entire dictionaries
  
  // Or even remove entire dictionary by index:
  dictionaryList.remove(10);