HashMap forEach(BiConsumer) method in Java with Examples

11 Oct, 2019
The forEach(BiConsumer) method of HashMap class perform the BiConsumer operation on each entry of hashmap until all entries have been processed or the action throws an exception. The BiConsumer operation is a function operation of the key-value pair of hashtable performed in the order of iteration. Method traverses each element of Hashtable until all elements have been processed by the method or an exception occurs. Exceptions thrown by the Operation are passed to the caller.
Syntax:
public void forEach(BiConsumer action)
Parameters: This method accepts a parameter action of BiConsumer type that represents what action are to be performed on the HashMap elements.
Returns: This method do not return anything.
Exceptions: This method throws NullPointerException if the action is null.
Below programs illustrate the forEach(BiConsumer) method:
Program 1: to traverse a hashmap using action
// Java program to demonstrate// forEach(BiConsumer) method.  import java.util.HashMap;import java.util.Map;import java.util.function.BiConsumer;  public class GFG {      // Main method    public static void main(String[] args)    {          // create a HashMap and add some values        Map<String, Integer> map            = new HashMap<>();          map.put("geeks", 55);        map.put("for", 13);        map.put("geeks", 22);        map.put("is", 11);        map.put("heaven", 90);        map.put("for", 100);        map.put("geekies like us", 96);          // creating a custom action        BiConsumer<String, Integer> action            = new MyBiConsumer();          // calling forEach method        map.forEach(action);    }}  // Defining Our Action in MyBiConsumer classclass MyBiConsumer implements BiConsumer<String, Integer> {      public void accept(String k, Integer v)    {        System.out.print("Key = " + k);        System.out.print("\t Value = " + v);        System.out.println();    }}
Key = geeks     Value = 22
Key = for     Value = 100
Key = is     Value = 11
Key = heaven     Value = 90
Key = geekies like us     Value = 96

Program 2:
// Java program to demonstrate// forEach(BiConsumer) method.  import java.util.HashMap;import java.util.Map;import java.util.function.BiConsumer;  public class GFG {      // Main method    public static void main(String[] args)    {          // Create a HashMap        // and add some values        Map<String, Integer> map            = new HashMap<>();          map.put("geeks", 55);        map.put("for", 13);        map.put("geeks", 22);        map.put("is", 11);        map.put("heaven", 90);        map.put("for", 100);        map.put("geekies like us", 96);          // creating an action        BiConsumer<String, Integer> action            = new MyBiConsumer();          // calling forEach method        map.forEach(action);    }}  // Defining Our Action in MyBiConsumer classclass MyBiConsumer implements BiConsumer<String, Integer> {      public void accept(String k, Integer v)    {        System.out.println("Key: " + k                           + "\tValue: " + v);          if ("for".equals(k)) {            System.out.println("Its the "                               + "highest value\n");        }    }}
Key: geeks    Value: 22
Key: for    Value: 100
Its the highest value

Key: is    Value: 11
Key: heaven    Value: 90
Key: geekies like us    Value: 96

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#forEach-java.util.function.BiConsumer-
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