HashTable forEach() method in Java with Examples Last Updated : 05 Jun, 2023 Comments Improve Suggest changes Like Article Like Report The forEach(BiConsumer) method of Hashtable class perform the BiConsumer operation on each entry of hashtable until all entries have been processed or the action throws an exception. The BiConsumer operation is a function operation of 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<? super K, ? super V> action) Parameters: This method takes a parameter name BiConsumer which represents the action to be performed for each element. Returns: This method returns nothing. Exception: This method throws: NullPointerException: if the specified action is null. Below programs illustrate the forEach(BiConsumer) method: Program 1: Java // Java program to demonstrate // forEach(BiConsumer) method. import java.util.*; public class GFG { // Main method public static void main(String[] args) { // create a table and add some values Map<String, Integer> table = new Hashtable<>(); table.put("Pen", 10); table.put("Book", 500); table.put("Clothes", 400); table.put("Mobile", 5000); table.put("Booklet", 2500); // add 100 in each value using forEach() table.forEach((k, v) -> { v = v + 100; table.replace(k, v); }); // print new mapping using forEach() table.forEach( (k, v) -> System.out.println("Key : " + k + ", Value : " + v)); } } Output:Key : Booklet, Value : 2600 Key : Clothes, Value : 500 Key : Mobile, Value : 5100 Key : Pen, Value : 110 Key : Book, Value : 600 Program 2: To Show NullPointerException Java // Java program to demonstrate // forEach(BiConsumer) method. import java.util.*; public class GFG { // Main method public static void main(String[] args) { // create a table and add some values Map<Integer, String> table = new Hashtable<>(); table.put(1, "100RS"); table.put(2, "500RS"); table.put(3, "1000RS"); try { // add 100 in each value using forEach() table.forEach((k, v) -> { v = v + 100; table.put(null, v); }); } catch (Exception e) { System.out.println("Exception: " + e); } } } Output:Exception: java.lang.NullPointerException References: https://docs.oracle.com/javase/8/docs/api/java/util/Hashtable.html#forEach-java.util.function.BiConsumer- Comment More infoAdvertise with us Next Article Hashtable computeIfAbsent() method in Java with Examples A AmanSingh2210 Follow Improve Article Tags : Java java-basics Java-Functions Java-HashTable Practice Tags : Java Similar Reads Hashtable in Java Hashtable class, introduced as part of the Java Collections framework, implements a hash table that maps keys to values. Any non-null object can be used as a key or as a value. To successfully store and retrieve objects from a hashtable, the objects used as keys must implement the hashCode method an 12 min read HashTable forEach() method in Java with Examples The forEach(BiConsumer) method of Hashtable class perform the BiConsumer operation on each entry of hashtable until all entries have been processed or the action throws an exception. The BiConsumer operation is a function operation of key-value pair of hashtable performed in the order of iteration. 2 min read Hashtable computeIfAbsent() method in Java with Examples The computeIfAbsent(Key, Function) method of Hashtable class which allows you to compute value of a mapping for specified key if key is not already associated with a value (or is mapped to null). If mapping function of this method returns null, then no mapping is recorded. 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