Java ConcurrentHashMap compute() Method

by Online Tutorials Library July 22, 2022

Java ConcurrentHashMap compute() Method

The compute() method of ConcurrentHashMap class is used to compute the mapping for the specified key and its current value.

Syntax

  public V compute(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.ConcurrentHashMap;   import java.util.*;   import java.util.function.BiFunction;      public class ConcurrentHashMapcomputeExample1 {           public static void main(String[] args)       {           Map chm = new ConcurrentHashMap();     //put is used to add value to map          chm.put(“1”, “1”);           chm.put(“2”, “10”);           chm.put(“3”, “100”);           chm.put(“4”, “2”);           chm.put(“5”, “20”);           chm.put(“6”, “200”);               System.out.println(“Values in map with detail: n”                             + chm.toString());             chm.compute(“6”, (key , val)                                    -> val + 100);           System.out.println(“Map after using  compute(): ”                                        + chm);       }  }  ,>,>

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Output:

Values in map with detail:   {1=1, 2=10, 3=100, 4=2, 5=20, 6=200}  Map after using  compute(): {1=1, 2=10, 3=100, 4=2, 5=20, 6=200100}

Example 2

  import java.util.concurrent.*;       public class ConcurrentHashMapcomputeExample2 {           public static void main(String[] args)       {           ConcurrentHashMap               conmap = new ConcurrentHashMap<>();           conmap.put(1, “Java”);           conmap.put(2, “php”);           conmap.put(3, “.net”);           System.out.println(“ConcurrentHashMap value detail: ”                             + conmap.toString());           conmap.compute(2, (key, val)                              -> val.concat(” (Angular)”));           conmap.compute(3, (key, val)                              -> val.concat(” (java Script)”));                     System.out.println(“New ConcurrentHashMap after compute: ”                             + conmap);       }   }  ,>

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Output:

ConcurrentHashMap value detail: {1=Java, 2=php, 3=.net}  New ConcurrentHashMap after compute: {1=Java, 2=php (Angular), 3=.net (java Script)}

Next TopicJava ConcurrentHashMap

Java ConcurrentHashMap compute() Method

Java ConcurrentHashMap compute() Method

Syntax

Parameter

Returns

Throws

Example 1

Example 2

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