Java 8 BiConsumer Examples
In Java 8, BiConsumer is a functional interface; it takes two arguments and returns nothing.
@FunctionalInterface
public interface BiConsumer<T, U> {
void accept(T t, U u);
}
Further Reading – Java 8 Consumer Examples
1. BiConsumer
JavaBiConsumer1.java
package com.mkyong.java8;
import java.util.function.Consumer;
public class JavaBiConsumer1 {
public static void main(String[] args) {
BiConsumer<Integer, Integer> addTwo = (x, y) -> System.out.println(x + y);
addTwo.accept(1, 2); // 3
}
}
Output
3
2. Higher Order Function
2.1 This example accepts BiConsumer
as an argument, create a generic addTwo
to join two objects.
JavaBiConsumer2.java
package com.mkyong.java8;
import java.util.function.BiConsumer;
public class JavaBiConsumer2 {
public static void main(String[] args) {
addTwo(1, 2, (x, y) -> System.out.println(x + y)); // 3
addTwo("Node", ".js", (x, y) -> System.out.println(x + y)); // Node.js
}
static <T> void addTwo(T a1, T a2, BiConsumer<T, T> c) {
c.accept(a1, a2);
}
}
Output
3
Node.js
2.2 More BiConsumer
examples.
JavaBiConsumer3.java
package com.mkyong.java8;
import java.util.function.BiConsumer;
public class JavaBiConsumer3 {
public static void main(String[] args) {
math(1, 1, (x, y) -> System.out.println(x + y)); // 2
math(1, 1, (x, y) -> System.out.println(x - y)); // 0
math(1, 1, (x, y) -> System.out.println(x * y)); // 1
math(1, 1, (x, y) -> System.out.println(x / y)); // 1
}
static <Integer> void math(Integer a1, Integer a2, BiConsumer<Integer, Integer> c) {
c.accept(a1, a2);
}
}
Output
2
0
1
1
3. Map.forEach
In the JDK source code, Map.forEach
accepts a BiConsumer
as an argument.
Map.java
default void forEach(BiConsumer<? super K, ? super V> action) {
Objects.requireNonNull(action);
for (Map.Entry<K, V> entry : entrySet()) {
K k;
V v;
try {
k = entry.getKey();
v = entry.getValue();
} catch (IllegalStateException ise) {
// this usually means the entry is no longer in the map.
throw new ConcurrentModificationException(ise);
}
action.accept(k, v);
}
}
JavaMapBiConsumer.java
package com.mkyong.java8;
import java.util.LinkedHashMap;
import java.util.Map;
public class JavaMapBiConsumer {
public static void main(String[] args) {
Map<Integer, String> map = new LinkedHashMap<>();
map.put(1, "Java");
map.put(2, "C++");
map.put(3, "Rust");
map.put(4, "JavaScript");
map.put(5, "Go");
map.forEach((k, v) -> System.out.println(k + ":" + v));
}
}
Output
1:Java
2:C++
3:Rust
4:JavaScript
5:Go
References
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