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Java ConcurrentHashMap | clear()
  • Last Updated : 29 Aug, 2018

Prerequisite : ConcurrentHashmap Java

clear() method
The java.util.concurrentHashMap.clear() method is used to clear the mapping. It is used to remove the mapping from ConcurrentHashMap.

Syntax:

public void clear()




// Java program to demonstrate
// clear() method
  
import java.util.concurrent.ConcurrentHashMap;
import java.util.*;
  
public class ConcurrentHashMapExample {
  
    public static void main(String[] args)
    {
  
        // Creating a ConcurrentHashMap
        Map<String, String> my_cmmap = new ConcurrentHashMap<String, String>();
  
        // Inserting mappings in ConcurrentHashMap
        // with the help of put() method
        my_cmmap.put("1", "1");
        my_cmmap.put("2", "1");
        my_cmmap.put("3", "1");
        my_cmmap.put("4", "1");
        my_cmmap.put("5", "1");
        my_cmmap.put("6", "1");
  
        // Print the ConcurrentHashMap
        System.out.println("Map before use of clear(): \n"
                           + my_cmmap);
  
        // Now clear the map using clear()
        my_cmmap.clear();
  
        // Print the clea Map
        System.out.println("Map after use of clear(): "
                           + my_cmmap);
    }
}
Output:
Map before use of clear(): 
{1=1, 2=1, 3=1, 4=1, 5=1, 6=1}
Map after use of clear(): {}

Example 2:




// Java program to demonstrate
// clear() method
  
import java.util.concurrent.ConcurrentHashMap;
import java.util.*;
  
public class ConcurrentHashMapExample {
  
    public static void main(String[] args)
    {
        // Creating a ConcurrentHashMap
        Map<String, String> my_map = new ConcurrentHashMap<String, String>();
  
        // Inserting mappings in ConcurrentHashMap
        // with the help of put() method
        my_map.put("Geeks", "100");
        my_map.put("Geek2", "150");
        my_map.put("Geeks3", "120");
        my_map.put("Geek4", "111");
        my_map.put("Geek5", "110");
        my_map.put("Geek6", "100");
  
        // Print the ConcurrentHashMap
        System.out.println("Map before use of clear(): \n"
                           + my_map);
  
        // Now clear the map using clear()
        my_map.clear();
  
        // Print the cleared Map
        System.out.println("Map after use of clear(): "
                           + my_map);
    }
}
Output:
Map before use of clear(): 
{Geeks3=120, Geek6=100, Geek5=110, Geek4=111, Geeks=100, Geek2=150}
Map after use of clear(): {}

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