HashTable compute() method in Java with Examples Last Updated : 02 Jun, 2023 Comments Improve Suggest changes Like Article Like Report The compute(Key, BiFunction) method of Hashtable class allows to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping is found). If the remapping function passed in compute() of Hashtable returns null as a return value then the mapping is removed from Hashtable(or remains absent if initially absent).If the remapping function throws an exception, the exception is rethrown, and the current mapping is left unchanged.During computation, modification this map using this method is not allowed.The compute() method can be used to update an existing value inside Hashtable. For example, This mapping append string value of mapping:Hashtable.compute(key, (k, v) -> v.append("strValue"))This method will throw a ConcurrentModificationException if the remapping function modified this map during computation. Syntax: public V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) Parameters: This method accepts two parameters: key: key with which the value is to be associated.remappingFunction: function to do the operation on value. Returns: This method returns new value associated with the specified key, or null if none. Exception: This method throws: ConcurrentModificationException: if it is detected that the remapping function modified this map. Below programs illustrate the compute(Key, BiFunction) method: Program 1: Java // Java program to demonstrate // compute(Key, BiFunction) 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); // print map details System.out.println("hashTable: " + table.toString()); // remap the values of hashTable // using compute method table.compute("Pen", (key, val) -> val + 15); table.compute("Clothes", (key, val) -> val - 120); // print new mapping System.out.println("new hashTable: " + table); } } Output:hashTable: {Book=500, Mobile=5000, Pen=10, Clothes=400} new hashTable: {Book=500, Mobile=5000, Pen=25, Clothes=280} Program 2: Java // Java program to demonstrate // compute(Key, BiFunction) 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"); // print map details System.out.println("hashTable: " + table.toString()); // remap the values of hashTable // using compute method table.compute(3, (key, val) -> val.substring(0, 4) + "00RS"); table.compute(2, (key, val) -> val.substring(0, 2) + "$"); // print new mapping System.out.println("new hashTable: " + table); } } Output:hashTable: {3=1000RS, 2=500RS, 1=100RS} new hashTable: {3=100000RS, 2=50$, 1=100RS} References: https://docs.oracle.com/javase/10/docs/api/java/util/Hashtable.html#compute(K, java.util.function.BiFunction) Comment More infoAdvertise with us Next Article HashTable compute() method in Java with Examples A AmanSingh2210 Follow Improve Article Tags : Java Java-Collections Java - util package java-basics Java-Functions Java-HashMap +2 More Practice Tags : JavaJava-Collections Similar Reads 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). 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