哈希图中不必要重复的值

Question

Main computation:

for (String keyElement : mKeys) {

            int index = str_mFormatedString.indexOf(keyElement);
            sendTheDataToMap(keyElement, page, index);

            while (index >= 0) {  // indexOf returns -1 if no match found
                index = str_mFormatedString.indexOf(keyElement, index + 1);


                if (index >= 0) {
                    sendTheDataToMap(keyElement, page, index);
                }
            }
        }

sendDataToMap function:

private void sendTheDataToMap(String key, int page, int index) {
    Pair mPair = new Pair(page, index);
    map.putIfAbsent(key, new ArrayList<>());
    map.get(key).add(mPair);
    //  System.out.println("Entry added to the map....");
}

Readmap function:

 private void readMap() {
    for (Map.Entry<String, ArrayList<Pair<Integer, Integer>>> ee : map.entrySet()) {
        String key = ee.getKey();
        ArrayList<Pair<Integer, Integer>> values = ee.getValue();
        // Process the values

        System.out.print(key + " | ");
        for (Pair value : values)
            System.out.print(" " + value.getPage() + "." + value.getIndex());
        System.out.println();
    }
}

Approach is simple, I read the multiple indices of a key from string and add it in to the map with String,ArrayList<Pair<Integer, Integer>> . I know I have done some small mistake either in main computation or while reading the map that is resulting in duplication of values.

Example output:

can | 5.167 5.223 5.167 5.223 7.157 7.338 7.751 7.157 7.338 7.751 7.157 7.338 7.751 15.558 16.209 16.436

Highlighted is repeating part.

Point is, I don't wanna write multiple values at first place and if that's not happening here then I don't wanna read multiple values.

Any help?

Edit 1: Inputs: A string (basically any string) which is being slipt on space. For ex: Hello how are you? => ['Hello','how','are','you?']

One line before Main computation:

 mKeys = splitTextToArray(str_mFormatedString);

and the function splitTextToArray()

private ArrayList<String> splittingTextToArray(String formattedTextInput) {
    String[] tempKeys = formattedTextInput.split("\\s+");

    //convert to Arraylist
    ArrayList<String> mKeys = new ArrayList<>(Arrays.asList(tempKeys));
    return mKeys;
}

Answer 1

Use a Set instead of a List for your map values to avoid duplicates:

Map<String, Set<Pair<Integer, Integer>>> map = new HashMap<>();
// ...
map.putIfAbsent(key, new HashSet<>()); // Or LinkedHashSet to preserve insertion order
map.get(key).add(mPair);

If you're really hell-bent on using a list, check whether the list doesn't already contain the value before adding it:

Map<String, List<Pair<Integer, Integer>>> map = new HashMap<>();
// ...
map.putIfAbsent(key, new ArrayList<>());

if (!map.get(key).contains(mPair)) {
    map.get(key).add(mPair);
}

// probably should optimize this to get rid of the multiple calls to map.get(key)

Have to make sure that equals() and hashCode() are correctly implemented for your Pair class though.

Answer 2

Arraylist can contain duplicate values so you can either use Set or check it before put to arraylist like below.

1) Declare Set instead of Arraylist

map.putIfAbsent(key, new HashSet<>());

or

2) check before add in arralist. (for this you need to overwrite hascode and equals in Pair Class.)

private void sendTheDataToMap(String key, int page, int index) {
    Pair mPair = new Pair(page, index);
    map.putIfAbsent(key, new ArrayList<>());
  if(!map.get(key).contains(mPair){
    map.get(key).add(mPair);
    //  System.out.println("Entry added to the map....");
  }
}