java8里面consumer&BiConsumer也是函数式接口，从代码上看，consumer只有一个入参，没有返回值；BiConsumer两个入参，没有返回值。

1、Consumer简单例子

package com.cattles.function;

import java.util.function.Consumer;

/**
 * @author cattle -  稻草鸟人
 * @date 2020/4/12 下午3:04
 */
public class Java8Consumer1 {

    public static void main(String[] args) {
        Consumer<String> stringConsumer = x -> System.out.println("hello!" + x);
        stringConsumer.accept("cattle");
    }
}

输出:

hello!cattle

2、Consumer当做参数传输

package com.cattles.function;

import java.util.Arrays;
import java.util.List;
import java.util.function.Consumer;

/**
 * @author cattle -  稻草鸟人
 * @date 2020/4/12 下午3:13
 */
public class Java8Consumer2 {

    public static void main(String[] args) {
        List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8);
        Consumer<Integer> integerConsumer = x -> System.out.println(x);
        forEach(integers, integerConsumer);
        System.out.println("===========");
        forEach(integers, x -> System.out.println(x));
    }

    static <T> void forEach(List<T> list, Consumer<T> consumer) {
        list.forEach(consumer);
    }
}

输出：

1
2
3
4
5
6
7
8
===========
1
2
3
4
5
6
7
8

3、BiConsumer简单例子

package com.cattles.function;

import java.util.function.BiConsumer;

/**
 * @author cattle -  稻草鸟人
 * @date 2020/4/12 下午3:20
 */
public class Java8BiConsumer1 {
    public static void main(String[] args) {
        BiConsumer<Integer, Integer> add = (x, y) -> System.out.println(Math.addExact(x, y));
        add.accept(1, 2);
    }
}

输出

3

4、BiConsumer当做参数传输

package com.cattles.function;

import java.util.function.BiConsumer;

/**
 * @author cattle -  稻草鸟人
 * @date 2020/4/12 下午3:23
 */
public class Java8BiConsumer2 {

    public static void main(String[] args) {
        add(1, 2, (x, y) -> System.out.println(x + y));
        add("Hello!", "Cattle", (x, y) -> System.out.println(x + y));
    }

    static <T> void add(T a, T b, BiConsumer<T, T> c) {
        c.accept(a, b);
    }
}

输出:

3
Hello!Cattle

５、Map.forEach例子

在第２点，consumer当做参数例子里面，我们发现list的forEach代码参数是Consumer，而map里面的forEach参数则使用的是BiConsumer，下面我们看下例子

package com.cattles.function;

import java.util.HashMap;

/**
 * @author cattle -  稻草鸟人
 * @date 2020/4/12 下午3:30
 */
public class Java8BiConsumer3 {

    public static void main(String[] args) {
        HashMap<Integer, String> map = new HashMap<>();
        map.put(1, "Java");
        map.put(2, "Kotlin");
        map.put(3, "React");
        map.put(4, "Python");
        map.put(5, "Go");
        map.forEach((k, v) -> System.out.println(k + ":" + v));
    }
}

输出:

1:Java
2:Kotlin
3:React
4:Python
5:Go