Is there a way to create an object with object name from the value of a string

Question

class states{

    List<String> cities = new ArrayList<String>();

    public void add_city(String current_city){
        this.cities.add(current_city);
    }
}

class add_values{

    public static void main(String [] args){
        System.out.println("Enter the state name : ");
        Scanner sc = new Scanner(System.in);
        String user_state = sc.nextLine(); // need to create an object with the name from a string value
        states user_state = new states();
        ....
        ....
    }
}

Is there a way to create an object for a class with the name from a string.

If, user enters the state name as "Michigan", an object is created with "Michigan" which is got from scanner. and cities can be added for the state Michigan.

Yes, trying to create object with name from the value of the string (here from the user) — Krish13287, Dec 01 '14 at 04:21
Again, objects don't have names, and you are confusing objects with variables, a core distinction in Java. — Hovercraft Full Of Eels, Dec 01 '14 at 04:23
The correct answer to questions like this is usually `HashMap`. — Dawood ibn Kareem, Dec 01 '14 at 04:29
@DavidWallace: I agree, but looking at his code, it appears that his issue is a lot simpler than that, that all he needs is a String name field for his State class thereby giving his State objects "names". Or maybe I'm over-simplifying -- time will tell. — Hovercraft Full Of Eels, Dec 01 '14 at 04:41
Yeah, the question is far from clear. I want to know what _an object is created with "Michigan"_ means. — Dawood ibn Kareem, Dec 01 '14 at 04:58

Hovercraft Full Of Eels · Accepted Answer · 2014-12-01T04:28:03.770

4

You will want to understand that objects have no names -- none, zero, zip. Yes, variables can have names, but that is not the same, since two or more variables can refer to the same object, and when that happens, which name is the name for the object? Again, neither/none since objects don't have names. As for variable names, they're way less important than you believe and almost don't exist in compiled code. What is most important are object references. Here an object can be associated with a String by means of a Map such as a HashMap<String, String> which is similar to an array or ArrayList that uses a String as its index rather than a number.

Now having said this, you can give your State class a String name field, and this may serve your purposes well.

i.e.,

import java.util.ArrayList;
import java.util.List;

public class State {
   private String name;
   private List<String> cities = new ArrayList<>();

   public State(String name) {
      this.name = name;
   }

   public String getName() {
      return name;
   }

   public void addCity(String city) {
      cities.add(city);
   }

   public List<String> getCities() {
      return cities;
   }

   @Override
   public String toString() {
      return "State of " + name + ", Cities: " + cities;
   }

}

Which can be run like:

public class StateTest {
   public static void main(String[] args) {
      State illinois = new State("Illinois"); 
      illinois.addCity("Chicago");
      illinois.addCity("Peoria");
      illinois.addCity("Springfield");

      System.out.println(illinois);
   }
}

edited Dec 01 '14 at 04:28

answered Dec 01 '14 at 04:21

Hovercraft Full Of Eels

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I think he meant creating an object of a class that he will get its name from the user, i.e. `Class.forName("com.package.MyClass").newInstance();` – Eng.Fouad Dec 01 '14 at 04:23
@Eng.Fouad: no, I think he's trying to do what I believe is possible in PHP -- where you can create a variable name with a string, but Java isn't PHP, and when coding in Java, one needs to understand and abide by the ways of Java. – Hovercraft Full Of Eels Dec 01 '14 at 04:26
@Eng.Fouad: Yeh, That is what i am trying to do. – Krish13287 Dec 01 '14 at 04:30
@Krish13287: really? You're trying to load a class from disk based on a name? Are you sure? – Hovercraft Full Of Eels Dec 01 '14 at 04:32
1

@Krish13287 So `Michigan` is the name of one of your classes? That DOES sound like an interesting design. – Dawood ibn Kareem Dec 01 '14 at 04:34
@DavidWallace Given that they named their `states` variable `user_state`, which is the name of the `String` variable, I'm pretty sure that's not the case. – Sotirios Delimanolis Dec 01 '14 at 04:45

score 0 · Answer 2 · answered Dec 01 '14 at 04:33

You can do something different using HashMap. Hope this will help to achieve your goal. Here is the code:

class States{

    List<String> cities = new ArrayList<String>();

    public void add_city(String current_city){
        this.cities.add(current_city);
    }
}

class add_values{

    public static void main(String [] args){
        HashMap<String, States> userStatesMap = new HashMap<String, States>();
        System.out.println("Enter the state name : ");
        Scanner sc = new Scanner(System.in);
        String user_state = sc.nextLine(); // need to create an object with the name from a string value
        userStatesMap.put(user_state, new states());

        ....
        ....
    }
}

Is there a way to create an object with object name from the value of a string

2 Answers2