Singleton Pattern with synchronization:
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// Java code to explain double check locking public class GFG {   // private instance, so that it can be   // accessed by only by getInstance() method   private static GFG instance;   private GFG()   {     // private constructor   }   public static GFG getInstance()   {     if (instance == null)     {       //synchronized block to remove overhead       synchronized (GFG.class)       {         if(instance==null)         {           // if instance is null, initialize           instance = new GFG();         }               }     }     return instance;   } } --------------------------------------------------------------------- Check that the variable is initialized (without obtaining the lock). If it is initialized, return it immediately. Obtain the lock. Double-check whether the variable has already been initialized: if another thread acquired the lock first, it may have already done the initialization. If so, return the initialized variable. Otherwise, initialize and return the variable.