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javaandroidmultithreadingcollectionssynchronized

Synchronize access to HashMap from two threads in java

I have two threads running ( One is Main Thread(Say Thread1) and another one is background thread (say Thread2)). I can access HashMap variable hashMap from Thread1 and Thread2. Thread1 modifies the hashMap and Thread2 reads the HashMap.

In Thread1 code will be:

synchronized(hashMap){
   //updating hashMap 
}

In Thread2 code will be:

synchronized(hashMap){
     //reading hashMap
}

Can I synchronize the access to hashMap using synchronized block in this way?

Solution

  • Yes. But also you can use Collections.synchronizedMap utility method to make a hashmap thread safe:

    Map yourMap = new HashMap();
Map synchronizedMap = java.util.Collections.synchronizedMap(yourMap);

    Or you can use ConcurrentHashMap or Hashtable which are thread safe by default.