Java 8 学习笔记

整理 Java 8 的新特性。

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lambda 匿名函数
函数式接口 Java 8 : 函数式接口注解 FunctionalInterface Java 8 : 函数式接口 Runnable : 无参数, 无返回值 Java 8 : 函数式接口 Callable : 无参数, 有返回值 Java 8 : 函数式接口 Supplier : 无参数, 有返回值 Java 8 : 函数式接口 Consumer : 1个参数, 无返回值 Java 8 : 函数式接口 Function : 1个参数, 有返回值 Java 8 : 函数式接口 BiFunction : 2个参数, 有返回值
函数引用 Java 8 : 函数引用

Java 8 : 函数式接口 Consumer : 1个参数, 无返回值


本文关键词:Java 8, 函数式接口,lambda 。

介绍

全路径: java.util.function.Consumer 。

Java 8 中引入。

源码:

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); };
    }
}

示例

代码示例:

import java.util.function.Consumer;

public class Main {

    public static void main(String[] args) {
        Consumer<Long> consumer = num -> {
            System.out.println("参数是: " + num);
        };

        consumer.accept(123L);
    }

}

执行结果:

参数是: 123

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