I'm new to Java. I'm wondering what will be the best option to store 2D array with different type of data.
It will be table of countries, each has capital and is in cotinent. Then I have to store it this way: ContinentID | Country name | Capital
What to choose?
You might want to consider making a Country class to hold this data, and then maintaining a list/array of instances of this class.
public class Country {
private int continentId;
private String name;
private String capital;
public Country(int continentId, String name, String capital) {
this.continentId = continentId;
this.name = name;
this.capital = capital;
}
// ...
}
You would then have something along the lines of
List<Country> countries = new ArrayList<Country>();
countries.add(new Country(123, "USA", "Washington DC"));
...
id refers to the continent ID.
create a country class with the needed attributes, then create a list, type it as country:
list<Country> clist = new ArrayList<Country>();
or any list you want. Now just store country objects in the list.
If continent id is just a sequence and does not add any specific meaning, you might want to consider a HashMap with key as country name and value as Capital. If order is important, consider a LinkedHashMap.
If continent id does carry meaning, then you might want to consider moving all the variables to a class, say Country and hold it in a list. If you are planning to retrieve by country name and not iterate, you might want to consider storing the objects in a Hashmap, with key as your country name or capital or whatever suits your need. The reason for a HashMap and not a list is that membership check on a List gives linear performance as against a constant time access on a HashMap.
HashMap<Integer, HashMap<String, String>>();
HashMap hm = new HashMap<Integer, HashMap<String, String>>(); ... and this is the complete code with parameterization: HashMap<Integer, HashMap<String, String>> hm = new HashMap<Integer, HashMap<String, String>>();<> parameter.HashMap<Integer, HashMap<String, String>> hm = new HashMap<>();? Interesting, did not know that. Thanks!
List<Country>whereCountryis an object containing the data for each country. Possibly aMap<String,Country>if you need to search by country name. I'm not sure what you mean by 2D in this context. Can you please clarify?