java8 Supplier接口和Consumer接口

java Terry 158浏览 1评论

Supplier接口

package java.util.function;

/**
 * Represents a supplier of results.
 *
 * <p>There is no requirement that a new or distinct result be returned each
 * time the supplier is invoked.
 *
 * <p>This is a <a href="package-summary.html">functional interface</a>
 * whose functional method is {@link #get()}.
 *
 * @param <T> the type of results supplied by this supplier
 *
 * @since 1.8
 */
@FunctionalInterface
public interface Supplier<T> {

    /**
     * Gets a result.
     *
     * @return a result
     */
    T get();
}

supplier接口只有一个抽象方法get(),通过get方法产生一个T类型实例。

实例:

package me.yanand;

import java.util.function.Supplier;

public class TestSupplier {
    public static void main(String[] args) {
        Supplier<Apple> appleSupplier = Apple::new;
        System.out.println("--------");
        appleSupplier.get();
    }
}

class Apple{
    public Apple() {
        System.out.println("创建实例");
    }
}

Consumer接口

package java.util.function;

import java.util.Objects;

/**
 * Represents an operation that accepts a single input argument and returns no
 * result. Unlike most other functional interfaces, {@code Consumer} is expected
 * to operate via side-effects.
 *
 * <p>This is a <a href="package-summary.html">functional interface</a>
 * whose functional method is {@link #accept(Object)}.
 *
 * @param <T> the type of the input to the operation
 *
 * @since 1.8
 */
@FunctionalInterface
public interface Consumer<T> {

    /**
     * Performs this operation on the given argument.
     *
     * @param t the input argument
     */
    void accept(T t);

    /**
     * Returns a composed {@code Consumer} that performs, in sequence, this
     * operation followed by the {@code after} operation. If performing either
     * operation throws an exception, it is relayed to the caller of the
     * composed operation.  If performing this operation throws an exception,
     * the {@code after} operation will not be performed.
     *
     * @param after the operation to perform after this operation
     * @return a composed {@code Consumer} that performs in sequence this
     * operation followed by the {@code after} operation
     * @throws NullPointerException if {@code after} is null
     */
    default Consumer<T> andThen(Consumer<? super T> after) {
        Objects.requireNonNull(after);
        return (T t) -> { accept(t); after.accept(t); };
    }
}

一个抽象方法accept(T t)定义了要执行的具体操作;注意看andThen方法,接收Consumer<? super T>类型参数,返回一个lambda表达式,此表达式定义了新的执行过程,先执行当前Consumer实例的accept方法,再执行入参传进来的Consumer实例的accept方法,这两个accept方法接收都是相同的入参t。

实例:

package me.yanand;

import java.util.function.Consumer;

public class TestConsumer {
    public static void main(String[] args) {
        Consumer<Integer> consumer = (t) -> {
            System.out.println(t*3);
        };
        Consumer<Integer> consumerAfter = (s) -> {
            System.out.println("之后执行:"+s);
        };
        consumer.andThen(consumerAfter).accept(5);
    }
}

转载请注明:Terry's blog » java8 Supplier接口和Consumer接口

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  1. 学习了
    匿名4周前 (07-29)回复