Java Adapter Pattern with ServiceProvider Example

This example's subject is example of adapter pattern.



When you need to a different service as like existing servisce behaviour, you can use adapter pattern.
This example, you use usa service, but you want to use europa service. However you say your service contract is UsaService. To use europa service, you use a Europa service adapter. This adapter implements usaservice but uses europage service inside. Example code is below.

package com.design.pattern.adapter;


public class UsaEuropaServiceAdapter {

    public static void main(String[] args) {

        User user;

        UsaService service = new UsaEuropaServiceAdapter.UsaServiceImpl();

        EuropaService europaService = new UsaEuropaServiceAdapter.EuropaServiceImpl();

        user = new UsaEuropaServiceAdapter.User();

        user.use(service);

//      service = new sil.EuropaServiceImpl(); this fails

        System.out.println("after adapter");

        service = new UsaEuropaServiceAdapter.EuropaServiceAdapter(europaService);

        user.use(service);

    }

    static class User{

        public void use(UsaService service){
            service.doSth();
        }
    }
   
    interface UsaService{
        void doSth();
    }

    static class UsaServiceImpl implements UsaService{

        @Override
        public void doSth() {
            System.out.println("USA service impl");
        }
    }


    interface EuropaService{
        void doAnotherThing();
    }

    static class EuropaServiceImpl implements EuropaService{


        @Override
        public void doAnotherThing() {
            System.out.println("Europa Service impl");
        }
    }

    static class EuropaServiceAdapter implements UsaService{

        private EuropaService service;

        public EuropaServiceAdapter(EuropaService service) {

            this.service = service;
        }

        @Override
        public void doSth() {

            service.doAnotherThing();
        }
    }
   
}