Java ConcurrentHashMap computeIfPresent() Method

by Online Tutorials Library July 22, 2022

Java ConcurrentHashMap computeIfPresent() Method

The computeIfPresent() method of ConcurrentHashMap class computes a new mapping given the key and its current mapped value If the value for the specified key is present.

Syntax

  public V computeIfPresent(K key, BiFunction<? super K,? super V,? extends V> remappingFunction)  

Parameter

key – key with which the specified value is to be associated

remappingFunction – the function to compute a value.

Returns

the new value associated with the specified key, or null if none

Throws

NullPointerException

IllegalStateException

RuntimeException

Example 1

    //import statement      import java.util.concurrent.*;     import java.util.*;     public class ConcurrentHashMapcomputeIfPresentExample1 {         public static void main(String[] args)       {           HashMap mapcon = new HashMap<>();           mapcon.put(“k1”, 100);           mapcon.put(“k2”, 200);           mapcon.put(“k3”, 300);           mapcon.put(“k4”, 400);               System.out.println(“HashMap values :n ” + mapcon.toString());              mapcon.computeIfPresent(“k4”, (key , val)  -> val + 100);                    mapcon.computeIfPresent(“k5”, (key , val)  -> val + 100);                   System.out.println(“New HashMap after computeIfPresent :n “+ mapcon);       }   }   ,>

Test it Now

Output:

HashMap values :   {k1=100, k2=200, k3=300, k4=400}  New HashMap after computeIfPresent :   {k1=100, k2=200, k3=300, k4=500}

Example 2

  import java.util.concurrent.*;       public class ConcurrentHashMapcomputeIfPresentExample2 {           public static void main(String[] args)       {           ConcurrentHashMap mapcon = new ConcurrentHashMap<>();           mapcon.put(“A”, 26);           mapcon.put(“B”, 98);           mapcon.put(“C”, 55);                  System.out.println(“ConcurrentHashMap values :n “+ mapcon.toString());             mapcon.computeIfPresent(“C”, (key , val)  -> val + 100);           System.out.println(“new ConcurrentHashMap after  computeIfPresent :n ” + mapcon);       }   }   ,>

Test it Now

Output:

ConcurrentHashMap values :   {A=26, B=98, C=55}  new ConcurrentHashMap after  computeIfPresent :   {A=26, B=98, C=155}

Next TopicJava ConcurrentHashMap

Java ConcurrentHashMap computeIfPresent() Method

Java ConcurrentHashMap computeIfPresent() Method

Syntax

Parameter

Returns

Throws

Example 1

Example 2

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