2021-07-21 Java 8 内置 4 大核心函数式接口

一、说明：

Java 8 内置 4 大核心函数式接口

二、代码：

import java.util.*;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;

public class TestFunctionalInterface {

    public static void main(String[] args) {

        FunctionalInterfaceDemo functionalInterfaceDemo = new FunctionalInterfaceDemo();
        functionalInterfaceDemo.execDemo();

    }

}

/**
 * Java 8 内置4大核心函数式接口
 * <p>
 * | Consumer<T>: 消费型接口
 * |     void accept(T t);
 * |
 * | Supplier<T>: 供给型接口
 * |     T get();
 * |
 * | Function<T, R>: 函数型接口
 * |     R apply(T t);
 * |
 * | Predicate<T>: 断言型接口
 * |     boolean test(T t);
 * |
 * </p>
 */
class FunctionalInterfaceDemo {

    private void consumerHandler(Double money, Consumer<Double> consumer) {
        consumer.accept(money);
    }

    private Set<Integer> supplierHandler(Supplier<Set<Integer>> supplier) {
        return supplier.get();
    }

    private String funcionHandler(String infoString, Function<String, String> function) {
        return function.apply(infoString);
    }

    private boolean predicateHandler(String name, Predicate<String> predicate) {
        return predicate.test(name);
    }

    public void execDemo() {

        //
        this.consumerHandler(100D, (money) -> System.out.println("本次消费：" + money + " 元。"));
        System.out.println("--------------------------------");
        System.out.println();

        //
        Set<Integer> integerSet = this.supplierHandler(() -> {
            Set<Integer> integers = new HashSet<>();
            for (int i = 0; i < 5; i++) {
                integers.add(new Random().nextInt());
            }
            return integers;
        });

        for (Integer integer : integerSet) {
            System.out.println(integer);
        }
        System.out.println("--------------------------------");
        System.out.println();


        //
        String trimString = this.funcionHandler("\t\t\t Hello World.    ", (str) -> str.trim());
        System.out.println(trimString);

        String subString = funcionHandler("我是一个函数", (str) -> str.substring(4, 6));
        System.out.println(subString);
        System.out.println("--------------------------------");
        System.out.println();

        //
        List<String> idCardsNumber = Arrays.asList("123X", "456X");
        for (String idCardNumber : idCardsNumber) {
            Boolean is = this.predicateHandler(idCardNumber, (idCard) -> "123X".equals(idCard));
            if (is) {
                System.out.println(idCardNumber + " 是我的身份证号。");
            } else {
                System.out.println(idCardNumber + " 不是我的身份证号。");
            }
        }
        System.out.println("--------------------------------");
        System.out.println();

    }

}

三、运行结果：

FunctionalInterface.png