Dynamic function calling in JDK8 with Predicate Object

Question

I have a class which call country specific functions for different use cases. I want to generalise the logic in such a way that if I specify the country name & the method name, the same method for that country's class gets executed.

Predicate Class:- https://docs.oracle.com/javase/8/docs/api/java/util/function/Predicate.html

private static void countrySpecificMethod(String countryName, Predicate predicate){
        if(countryName.equals("EGYPT")){
            // call the predicate function in EGYPT class
        } else if (countryName.equals("INDIA")) {
            // call the predicate function in INDIA class
        } else if (countryName.equals("HUNGARY")) {
            // call the predicate function in HUNGARY class
        } else if(countryName.equals("TURKEY")){
           // call the predicate function in TURKEY class
        } else if(countryName.equals("ITALY")){
            // call the predicate function in ITALY class
        } else if(countryName.equals("VIETNAM")){
            // call the predicate function in VIETNAM class
        } else{
           // call the predicate function in same class
        }
    }

Example:-

countrySpecificMethod("EGYPT", prepareAddress) 
 It should then call EGYPT.prepareAddress()

countrySpecificMethod("EGYPT", prepareUser)
 It should then call EGYPT.prepareUser()

Any help how this can be achieved?

https://docs.oracle.com/javase/8/docs/api/java/util/function/Predicate.html — Diksha Goyal, May 15 '23 at 11:28
That is not really useful. What are you trying to actually achieve? — aled, May 15 '23 at 11:34
Ohh got it, so I want to achieve a High order kind of Function here, where predicate for example can be `prepareAddress` & country be EGYPT. So the countrySpecificMethod should then call EGYPT.prepareAddress(); — Diksha Goyal, May 15 '23 at 11:39
I just wanted to show what I need to do. It obviously will be a function name — Diksha Goyal, May 16 '23 at 10:55
But a `Predicate` is not a function name. It’s not clear why you think this interface is suitable to your task at all. Which is one of the reasons why no-one understood your actual task so far. — Holger, May 22 '23 at 12:07

score 0 · Answer 1 · answered May 15 '23 at 13:43

You could have a lookup table to find the object from the appropiate class for the country, and lookup for the string identifier that matches the country.

For example a Map implementation, using a String as the key, and an interface or abstract class that defines the methods that can be called. It would look something like this:

Map<String, CountrySpecificInterface> countryLookup = new HashMap<tring, CountrySpecificInterface>();

countryLookup.put("EGYPT", new EgyptImplementation()); // EgyptImplementation implements CountrySpecificInterface including method prepareAddress()

countryLookup.get(countryName).prepareAddress()

You should put the string literals somewhere, to avoid repeating them all over the code. For example use an Enum.

Since Java 7, you can write `new HashMap<>()` instead of repeating the type arguments. — Holger, May 16 '23 at 10:24

Dynamic function calling in JDK8 with Predicate Object

1 Answers1