Question
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Can you provide an example of Java ConcurrentHashMap class: computeIfAbsent()?
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//import statement
import java.util.concurrent.*;
import java.util.*;
public class ConcurrentHashMapcomputeIfAbsentExample1_1 {
public static void main(String[] args)
{
// crete a HashMap and add some values
HashMap<String, Integer> 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.computeIfAbsent("k5", k -> 200 + 300);
mapcon.computeIfAbsent("k6", k -> 60 * 10);
System.out.println("New HashMap after computeIfAbsent :\n "+ mapcon);
}
}
Output:
HashMap values :
{k1=100, k2=200, k3=300, k4=400}
New HashMap after computeIfAbsent :
{k1=100, k2=200, k3=300, k4=400, k5=500, k6=600}
|
What is Java ConcurrentLinkedQueue Class?
|
ConcurrentLinkedQueue is an unbounded thread-safe queue which arranges the element in FIFO. New elements are added at the tail of this queue and the elements are added from the head of this queue.
|
What are the class methods of Java ConcurrentLinkedQueue?
|
Method: add()
Description: Inserts the specified element at the tail of this queue
Method: addAll()
Description: Inserts all the elements which are present in the specified collection to the tail of this queue
Method: contains()
Description: Returns true if this queue contains the specified element
Method: forEach()
Description: Performs the given action for each element until all elements have been processed.
Method: isEmpty()
Description: Returns true if this queue contains no elements.
Method: iterator()
Description: Returns an iterator over the elements in this queue
Method: offer()
Description: Inserts the specified element at the tail of this queue
Method: remove()
Description: Removes the specified element from this queue, if this element is present in the queue
Method: removeAll()
Description: Removes all the elements of this in queue which are present in the specified collection.
Method: removeIf()
Description: Removes all the elements in this queue that satisfy the given predicate filter.
Method: retainAll()
Description: Retain only those elements in this queue that are present in the specified collection.
Method: size()
Description: Returns the number of the elements in this queue.
Method: spliterator()
Description: Returns a spliterator over the elements in this queue.
Method: toArray()
Description: Returns an array containing all the elements of this queue which are in proper sequence.
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