How to synchronize Map

HashMap is non-synchronized in Java. So to perform thread-safe operations,you must synchronize HashMap.

There are two ways.

   1. Synchronizing the map explicitly. 

   2. Use 'Collections.synchronizedMap' method. 

import java.util.*;

public class MapEx {
    public static void main(String args[]){
        Map<Integer, Integer> map = Collections.synchronizedMap(new HashMap<>());
        
        map.put(1, 1*1);
        map.put(2, 2*2);
        map.put(3, 3*3);
        
        System.out.println(map);
    }
}

Output

{1=1, 2=4, 3=9}

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