Accessing a HashMap from a different class

Question

I have a hashmap in my class titled DataStorage:

HashMap people = new HashMap();

people.put(\"bob\", 2);
peopl         


        

Answer 1

If you need to share the same instance of a HashMap across your application, you need to create a singleton. Using a singleton guarantees that the same instance of the HashMap will always be referenced by anything trying to access it. For example for a HashMap:

Singleton class:

public class MyData {

    private static final MyData instance = new MyData ();

    private MyData () {     
            HashMap myDataMap = new HashMap();          
               ... logic to populate the map

            this.referenceData = myDataMap;

    }

    public HashMap referenceData;

    public static DeviceData getInstance(){
        return instance;
    }
}

Usage in another class:

HashMap referenceData = MyData.getInstance().referenceData;