Java ConcurrentHashMap replace() Method

by Online Tutorials Library July 22, 2022

Java ConcurrentHashMap replace() Method

The replace() method of ConcurrentHashMap class replaces the entry for a key only if it is currently mapped to some value.

Syntax

  public V replace(K key, V value)    public boolean replace(K key, V oldValue, V newValue)  

Parameter

key – key with which the specified value is associated

oldValue – value expected to be associated with the specified key

newValue – value to be associated with the specified key

Returns

true if the value was replaced

Throw

NullPointerException.

Example 1

  import java.util.concurrent.*;       import java.util.*;       public class  ConcurrentHashMapreplaceExample1 {           public static void main(String[] args)       {             // crete a HashMap and add some values           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());            //replace the value of key k1 to 1000          mapcon.replace(“k1” , 1000);          System.out.println(“New HashMap after remove :n “+ mapcon);       }   }   ,>

Test it Now

Output:

HashMap values :   {k1=100, k2=200, k3=300, k4=400}  New HashMap after remove :   {k1=1000, k2=200, k3=300, k4=400}

Example 2

  import java.util.concurrent.*;        import java.util.*;       public class  ConcurrentHashMapreplaceExample2 {           public static void main(String[] args)       {             // crete a HashMap and add some values           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());            //replace the value of key k2 to 2000          mapcon.replace(“k2” , 200 , 2000);          System.out.println(“New HashMap after remove :n “+ mapcon);       }   }   ,>

Test it Now

Output:

HashMap values :   {k1=100, k2=200, k3=300, k4=400}  New HashMap after remove :   {k1=100, k2=2000, k3=300, k4=400}

Next TopicJava ConcurrentHashMap

Java ConcurrentHashMap replace() Method

Java ConcurrentHashMap replace() Method

Syntax

Parameter

Returns

Throw

Example 1

Example 2

Java ConcurrentHashMap putIfAbsent() Method

Java Abstract Keyword

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