Question

I need some kind of data structure don’t know yet which would be most suitable.

Here is what I’m working with: I have a bunch rows of data processing and each row has its own country code.

I want to obtain as result how many times each country code repeats throughout the process.

Answer 1

You might try a HashMap. With a HashMap, you can use the country code as the key, and the count of how many times each appears as the value stored in that key. If you encounter a particular country code for the first time, insert it into the map with an initial value of 1; otherwise, increment the existing value.

HashMap<String, Integer> myMap = new HashMap<String, Integer>();

for (... record : records) {
    String countryCode = record.getCountryCode();

    int curVal;
    if (myMap.containsKey(countryCode)) {
        curVal = myMap.get(countryCode);
        myMap.put(countryCode, curVal + 1);
    } else {
        myMap.put(countryCode, 1);
    }
}

// myMap now contains the count of each country code, which
// can be used for whatever purpose needed.