Supplier وConsumer

ما الذي تفعله Supplier

import java.util.function.Supplier;

public class Main {
    public static void main(String[] args) {
        Supplier<String> greeting = () -> "Hello!";
        System.out.println(greeting.get());
    }
}

تتسم Suppliers بالكسل

import java.util.function.Supplier;

public class Main {
    public static void main(String[] args) {
        Supplier<Integer> expensive = () -> {
            System.out.println("computing...");
            return 42;
        };
        System.out.println("before get");
        System.out.println(expensive.get());
    }
}

Supplier للقيم الافتراضية

import java.util.Optional;

public class Main {
    public static void main(String[] args) {
        Optional<String> name = Optional.empty();
        System.out.println(name.orElseGet(() -> "default"));
    }
}

ما الذي تفعله Consumer

import java.util.function.Consumer;

public class Main {
    public static void main(String[] args) {
        Consumer<String> printer = s -> System.out.println("Got: " + s);
        printer.accept("data");
    }
}

Consumer مع forEach

import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> items = List.of("a", "b", "c");
        items.forEach(item -> System.out.println(item));
    }
}

تسلسل Consumers باستخدام andThen

import java.util.function.Consumer;

public class Main {
    public static void main(String[] args) {
        Consumer<String> first = s -> System.out.println("upper: " + s.toUpperCase());
        Consumer<String> second = s -> System.out.println("len: " + s.length());
        first.andThen(second).accept("hello");
    }
}

BiConsumer لمدخلين

import java.util.Map;

public class Main {
    public static void main(String[] args) {
        Map<String, Integer> ages = Map.of("Ann", 30, "Bob", 25);
        ages.forEach((name, age) -> System.out.println(name + "=" + age));
    }
}

مراجع الطرق بصفتها Consumers

import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<Integer> nums = List.of(1, 2, 3);
        nums.forEach(System.out::println);
    }
}

دمج Supplier وConsumer

import java.util.function.Supplier;
import java.util.function.Consumer;

public class Main {
    public static void main(String[] args) {
        Supplier<String> source = () -> "payload";
        Consumer<String> sink = s -> System.out.println("received " + s);
        sink.accept(source.get());
    }
}

إرجاع الكائنات من Supplier

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;

public class Main {
    public static void main(String[] args) {
        Supplier<List<String>> factory = ArrayList::new;
        List<String> list = factory.get();
        list.add("x");
        System.out.println(list);
    }
}

الآثار الجانبية مقابل الدوال النقية

import java.util.function.Supplier;
import java.util.function.Consumer;

public class Main {
    public static void main(String[] args) {
        Supplier<Integer> dice = () -> 4;
        Consumer<Integer> show = n -> System.out.println("rolled " + n);
        show.accept(dice.get());
    }
}

تحقّق سريع

مراجعة