How to insert user-inputted string to direct a reference?

Question

(In java,) This may or may not be possible, I assume it is because it seems to short-cutty/easy to not exist. Basically what I want to do is have the user insert the name of a state, then it add one to that state's counter, which is stored in a different class. I want to do this without creating 50 if/else statements. Here's pseudocode which represents how I would expect it to be done. (this code would be encapsuled in a while loop in mainclass.java and the counters and state names are in a class named state.java.)

Scanner userstate = new Scanner(System.in);
String statename = userstate.nextLine();

state.(statename).counter++;

in state.java:

 public state(int counter){
}
    public static state Alabama = new state(0);

For time's sake, I hope there is a shortcut similar to the above.

Answer 1

The preferred way in this case would be to store the states in a HashMap or similar. This allows you to look up a state by name:

import java.util.*;

class State
{
    static HashMap<String, State> states = new HashMap<String, State>();

    public static State Alabama = new State("Alabama", 0);

    public State(String name, int counter)
    {
        // [ init... ]
        states.put(name, this); // add this state to the collection of states
    }

    public static State getByName(String name)
    {
        return states.get(name);
    }
}

Then your code could look like this:

State.getByName(statename).counter++;

You could also use reflection , but that should be avoided where possible.

Answer 2

You don't want to try looking up variables by their Java names (eg, "Alabama"); this is possible but much more complicated than you want to deal with.

If you can use external libraries, this is a perfect fit for a Guava Multiset , which keeps track of how many times a certain element has been seen. Otherwise, you probably want a Map<String,Integer> from the state name to a counter. (Note that you'll have to put(get()+1) in that case; ++ won't work.)