The method Map.forEach(BiConsumer) performs the given action for each entry of the map until all are processed or exception is thrown.

The signature of the java.util.Map.forEach(BiConsumer) method is as follows:

default void forEach(BiConsumer<? super K,? super V> action)

The method is available since Java 8.

• BiConsumer<? super K, ? super V> action – action to be performed for each entry

The method takes BiConsumer that returns nothing.

• NullPointerException: when given action is null,
• ConcurrentModificationException: when entry is found to be removed during iteration.

In the following code we use java.util.Map.forEach(BiConsumer):

package com.farenda.java.util;

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

public class MapExamples {

    public static void main(String[] args) {
        Map<Integer,String> nameForId = new HashMap<>();
        nameForId.put(1, "Kajko");
        nameForId.put(2, "Kokosz");
        System.out.println("Original map: " + nameForId);

        System.out.println("Pre Java 8 for-each:");
        for (Entry<Integer,String> entry : nameForId.entrySet()) {
            System.out.printf("key: %d, value: %s%n",
                    entry.getKey(), entry.getValue());
        }

        System.out.println("Java 8 forEach:");
        nameForId.forEach((key,value) ->
                System.out.printf("key: %d, value: %s%n",
                        key, value));
    }
}

The above code produces the following output:

Original map: {1=Kajko, 2=Kokosz}
Pre Java 8 for-each:
key: 1, value: Kajko
key: 2, value: Kokosz
Java 8 forEach:
key: 1, value: Kajko
key: 2, value: Kokosz

• Java ForEach loop