Getting submap, headmap, and tailmap from Java TreeMap

Getting Synchronized Map from Java HashMap

Last Updated : 13 Jan, 2021

HashMap is a non synchronized collection class. If we want to perform thread-safe operations on it then we must have to synchronize it explicitly. In order to synchronize it explicitly the synchronizedMap() method of java.util.Collections class is used to return a synchronized (thread-safe) map backed by the specified map.

// Get synchronized map using Collections.synchronizedMap()

Map<Integer, String> synchrMap = Collections.synchronizedMap(hmap);

To iterate the synchronized map we use a synchronized block:

// Synchronized block
synchronized (synchrMap) {

      // Iterate synchronized map
      for (Map.Entry<Integer, String> entry : synchrMap.entrySet()) {

        // Print key : value
        System.out.println(entry.getKey() + " : " + entry.getValue());
        
      }
}

Implementation:

Java

// Java Program to demonstrate how  
// to get synchronized map from HashMap 
  
import java.util.*; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        // New HashMap 
        HashMap<Integer, String> hmap = new HashMap<>(); 
  
        // Add element to map 
        hmap.put(1, "Akshay"); 
        hmap.put(2, "Bina"); 
        hmap.put(3, "Chintu"); 
  
        // Get synchronized map using 
        // Collections.synchronizedMap() 
        Map<Integer, String> synchrMap = Collections.synchronizedMap(hmap); 
  
        System.out.println("Synchronized Map : "); 
  
        // Synchronized block 
        synchronized (synchrMap) 
        { 
  
            // Iterate synchronized map 
            for (Map.Entry<Integer, String> entry : 
                 synchrMap.entrySet()) { 
  
                // Print key : value 
                System.out.println(entry.getKey() + " : "
                                   + entry.getValue()); 
            } 
        } 
    } 
}

Output

Synchronized Map : 
1 : Akshay
2 : Bina
3 : Chintu

Getting submap, headmap, and tailmap from Java TreeMap

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