Funktsional interfeyslarga kirish

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Funktsional interfeyslarga kirish - Java 8 da qayta yaratilgan tushunchalar

Dunyodagi har bir Java dasturchisi kamida bir marta quyidagi interfeyslardan birini ishlatgan: java.lang.Runnable, java.awt.event.ActionListener, java.util.Comparator, java.util.concurrent.Callable. Ularning barchasida bitta umumiy narsa bor va bu ularning barchasida faqat bitta usul bor. JDK-da Java dasturchilari tomonidan yaratilgan boshqa ko'plab bunday interfeyslar mavjud. Single Abstract Method interfacesUshbu interfeyslar (SAM interfeyslari) deb ham ataladi . Ushbu interfeyslardan foydalanishning eng mashhur usullaridan biri quyidagi misolda bo'lgani kabi ushbu interfeyslardan foydalanadigan anonim ichki sinflarni yaratishdir:

public class AnonymousInnerClassTest {
    public static void main(String[] args) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("A thread created and running...");
            }
        }).start();
    }
}

Java 8 da SAM kontseptsiyasi qayta yaratiladi va funksional interfeyslar deb ataladi. Ular lambda ifodalari, usul havolalari va mos yozuvlar konstruktorlari yordamida ifodalanishi mumkin. Yangi @FunctionalInterface izohi yaratildi, u siz izoh bergan interfeys funksional darajada ishlamasa, kompilyator darajasida xatoliklarni chiqarish uchun ishlatiladi. Keling, bitta mavhum usul bilan oddiy funktsional interfeysni ko'rib chiqaylik:

@FunctionalInterface
public interface SimpleFunInterface {
    public void doWork();
}

Interfeys sinfdan mavhum usullarni ham e'lon qilishi mumkin java.lang.Object, ammo bu holda interfeys funktsional deb e'lon qilinishi ham mumkin:

@FunctionalInterface
public interface SimpleFuncInterface {
    public void doWork();
    public String toString();
    public Boolean equals(Object o);
}

Interfeysga boshqa mavhum usulni qo'shganingizdan so'ng, IDE uni rasmdagi kabi xato deb belgilaydi: Interfeys boshqa interfeysdan meros bo'lishi mumkin, agar interfeys funktsional interfeysdan meros bo'lsa va yangi mavhum usullarni o'z ichiga olmasa, u holda bu interfeys ham funktsional hisoblanadi. Ammo interfeys faqat bitta mavhum usul va ko'plab standart usullarni o'z ichiga olishi mumkin va u hali ham funktsional hisoblanadi.

@FunctionalInterface
public interface ComplexFunctionalInterface extends SimpleFuncInterface {
    default public void doSomeWork() {
        System.out.println("Doing some work in interface impl...");
    }
    default public void doSomeWork() {
        System.out.println("Doing some other work in interface impl...");
    }
}

Yuqori misol hali ham funktsional interfeysdir. Endi funktsional interfeyslarni amalga oshirish uchun anonim ichki sinfni almashtirish uchun lambda ifodalaridan qanday foydalanishimiz mumkinligini ko'rib chiqamiz:

/*
*Implementation the interface by creating an
*anonymoous inner class versus using
*lambda expression.
*/
public class SimpleFunInterfaceTest {
    public static void main(String[] args) {
        carryOutWork(new SimpleFunInterface() {
            @Override
            public void doWork() {
                System.out.println("Do work in SimpleFun impl...");
            }
        });
        carryOutWork(() -> System.out.println("Do work in lambda exp impl..."));
    }
    public static void carryOutWork(SimpleFuncInterface sfi) {
        sfi.work();
    }
}

Dasturning natijasi quyidagicha bo'ladi:

Do work in SimpleFun impl...
Do work in lambda exp impl...

Agar siz Java lambda ifodasi sintaksisini qo'llab-quvvatlaydigan IDE dan foydalanayotgan bo'lsangiz (Netbeans 8 Nightly Builds) - Anonim ichki sinflardan foydalanishda sizga maslahat beriladi: Bu Java 8-dagi funktsional interfeyslar tushunchasi va ularni qanday amalga oshirish mumkinligi haqida qisqacha ma'lumot edi. lambda ifodalaridan foydalanish.