Java HashMap associative multi dimensional array can not create or add elements

Question

Okay so I have spent several hours trying to wrap my head around this concept of a HashMap in Java but am just not able to figure it out. I have looked at many tutorials but

Answer 1

HashMap<String, HashMap<String, String>> myArray = new HashMap<String, HashMap<String, String>>();
HashMap<String, String> value = new HashMap<String, String>();
value.put("name", "English name");
value.put("desc", "English description");
value.put("keys", "English keywords");

myArray.put("en" , value);

value = new HashMap<String, String>();
value.put("name", "French name");
value.put("desc", "French description");
value.put("keys", "French keywords");

myArray.put("fr" , value);

Answer 2

Unfortunately, there's no concise syntax for constructing populated maps in Java. You'll have to write it out long-hand. A separate helper method can make it a little simpler:

HashMap<String, String> makeMap(String name, String desc, String keys) {
    HashMap<String, String> map = new HashMap<>();
    // Before Java 7, above must be: new HashMap<String, String>();
    map.put("name", name);
    map.put("desc", desc);
    map.put("keys", keys);
}

Then:

HashMap<String, HashMap<String, String>> myArray = new HashMap<>();
myArray.put("en",
    makeMap("english name", "english description", "english keywords"));
// etc.

You would retrieve it with:

english_name = myArray.get("en").get("name");

Answer 3

HashMap<String, HashMap<String, String>> myArray = new HashMap<String, HashMap<String, String>>();

if (!myArray.containsKey("en")) {
    myArray.put("en", new HashMap<String, String>());
}
myArray.get("en").put("name", "english name");

In Java you have to be explicit about when you are creating an object. In this case first we check if there is already a HashMap object stored in our outer HashMap under the key "en". If not, we create an empty one.

Now to put a new value into it we have to first get it from the outer HashMap, then put the new value.

Answer 4

import java.util.HashMap;
public class Main
{
    public static void main(String[] args) {
        // Creating array
        HashMap<String, HashMap<String, String>> myArray = new HashMap<String, HashMap<String, String>>();
        // Setting values
        for(int i=0; i<100;i++) {
            myArray.put("key1"+i, new HashMap<String, String>());
            myArray.get("key1"+i).put("key2"+i, "value"+i);
        }
        // Getting values
        for(int i=0; i<100; i++) {
        System.out.println(myArray.get("key1"+i).get("key2"+i));
        }
    }
}