Question

Given a specific set of strings, what’s the best way to map them to a corresponding set of integers? Say I have a class with a few integer constants that I use internally, but need to take incoming external strings and determine the correct corresponding integer constant they map to.

Here’s a simplified example:

public class Example {
    public static final int ITEM_APPLE = 0;
    public static final int ITEM_BANANA = 1;
    public static final int ITEM_GRAPE = 3;

    public void incomingData(String value) {
        // Possible values would be "apple", "banana", and "grape" in this case.
    }
}

What would the most appropriate approach be to go from that value to its corresponding integer constant? A HashMap? Or is ther any way to define these mappings in a static member? Another idea?

Answer 1

I would use a HashMap as that is closest to what you want to achieve, and therefore a maintainable solution. You can define a static HashMap:

Class Example {
    public static final int ITEM_APPLE = 0;
    public static final int ITEM_BANANA = 1;
    public static final int ITEM_GRAPE = 3;

    private static final Map<String, Integer> fruitCodes = new HashMap<String, Integer>();

    static {
        fruitCodes.put("apple", ITEM_APPLE);
        fruitCodes.put("banana", ITEM_BANANA);
        // ...
    }


    public void incomingData(String value) {
        // Possible values would be "apple", "banana", and "grape" in this case.
        Integer code = fruitCodes(value);

        if (null == code) {
            throw new IllegalArgumentException("Forbidden fruit: " + value);
        }
    }
}