Java8 Consumer&BiConsumer使用

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

1package com.cattles.function;
2
3import java.util.function.Consumer;
4
5/**
6 * @author cattle -  稻草鸟人
7 * @date 2020/4/12 下午3:04
8 */
9public class Java8Consumer1 {
10
11    public static void main(String[] args) {
12        Consumer<String> stringConsumer = x -> System.out.println("hello!" + x);
13        stringConsumer.accept("cattle");
14    }
15}
16

输出:

hello!cattle

2、Consumer当做参数传输

1package com.cattles.function;
2
3import java.util.Arrays;
4import java.util.List;
5import java.util.function.Consumer;
6
7/**
8 * @author cattle -  稻草鸟人
9 * @date 2020/4/12 下午3:13
10 */
11public class Java8Consumer2 {
12
13    public static void main(String[] args) {
14        List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8);
15        Consumer<Integer> integerConsumer = x -> System.out.println(x);
16        forEach(integers, integerConsumer);
17        System.out.println("===========");
18        forEach(integers, x -> System.out.println(x));
19    }
20
21    static <T> void forEach(List<T> list, Consumer<T> consumer) {
22        list.forEach(consumer);
23    }
24}
25

输出：

11
22
33
44
55
66
77
88
9===========
101
112
123
134
145
156
167
178
18

3、BiConsumer简单例子

1package com.cattles.function;
2
3import java.util.function.BiConsumer;
4
5/**
6 * @author cattle -  稻草鸟人
7 * @date 2020/4/12 下午3:20
8 */
9public class Java8BiConsumer1 {
10    public static void main(String[] args) {
11        BiConsumer<Integer, Integer> add = (x, y) -> System.out.println(Math.addExact(x, y));
12        add.accept(1, 2);
13    }
14}
15

输出

3

4、BiConsumer当做参数传输

1package com.cattles.function;
2
3import java.util.function.BiConsumer;
4
5/**
6 * @author cattle -  稻草鸟人
7 * @date 2020/4/12 下午3:23
8 */
9public class Java8BiConsumer2 {
10
11    public static void main(String[] args) {
12        add(1, 2, (x, y) -> System.out.println(x + y));
13        add("Hello!", "Cattle", (x, y) -> System.out.println(x + y));
14    }
15
16    static <T> void add(T a, T b, BiConsumer<T, T> c) {
17        c.accept(a, b);
18    }
19}
20

输出:

13
2Hello!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

1package com.cattles.function;
2
3import java.util.HashMap;
4
5/**
6 * @author cattle -  稻草鸟人
7 * @date 2020/4/12 下午3:30
8 */
9public class Java8BiConsumer3 {
10
11    public static void main(String[] args) {
12        HashMap<Integer, String> map = new HashMap<>();
13        map.put(1, "Java");
14        map.put(2, "Kotlin");
15        map.put(3, "React");
16        map.put(4, "Python");
17        map.put(5, "Go");
18        map.forEach((k, v) -> System.out.println(k + ":" + v));
19    }
20}
21

输出:

11:Java
22:Kotlin
33:React
44:Python
55:Go