Synchronized Block in Java

by Online Tutorials Library July 22, 2022

Synchronized Block in Java

Synchronized block can be used to perform synchronization on any specific resource of the method.

Suppose we have 50 lines of code in our method, but we want to synchronize only 5 lines, in such cases, we can use synchronized block.

If we put all the codes of the method in the synchronized block, it will work same as the synchronized method.

Points to Remember

Synchronized block is used to lock an object for any shared resource.
Scope of synchronized block is smaller than the method.
A Java synchronized block doesn’t allow more than one JVM, to provide access control to a shared resource.
The system performance may degrade because of the slower working of synchronized keyword.
Java synchronized block is more efficient than Java synchronized method.

Syntax

Example of Synchronized Block

Let’s see the simple example of synchronized block.

TestSynchronizedBlock1.java

  class Table  {       void printTable(int n){       synchronized(this){//synchronized block         for(int i=1;i<=5;i++){          System.out.println(n*i);          try{           Thread.sleep(400);          }catch(Exception e){System.out.println(e);}         }       }     }//end of the method    }        class MyThread1 extends Thread{    Table t;    MyThread1(Table t){    this.t=t;    }    public void run(){    t.printTable(5);    }        }    class MyThread2 extends Thread{    Table t;    MyThread2(Table t){    this.t=t;    }    public void run(){    t.printTable(100);    }    }        public class TestSynchronizedBlock1{    public static void main(String args[]){    Table obj = new Table();//only one object    MyThread1 t1=new MyThread1(obj);    MyThread2 t2=new MyThread2(obj);    t1.start();    t2.start();    }    }    

Output:

       5         10         15         20         25         100         200         300         400         500

Synchronized Block Example Using Anonymous Class

TestSynchronizedBlock2.java

  // A Sender class  class Sender   {     public void SenderMsg(String msg)    {       System.out.println(“nSending a Message: ”  + msg);      try      {         Thread.sleep(800);       }       catch (Exception e)       {         System.out.println(“Thread interrupted.”);       }       System.out.println(“n” +msg+ “Sent”);    }  }   // A Sender class for sending a message using Threads   class SenderWThreads extends Thread   {     private String msg;     Sender sd;       // Receiver method to receive a message object and a message to be sent     SenderWThreads(String m, Sender obj)    {       msg = m;      sd = obj;     }       public void run()     {       // Checks that only one thread sends a message at a time.       synchronized(sd)       {         // synchronizing the sender object         sd.SenderMsg(msg);      }     }   }   // Driver Code   public class ShynchronizedMultithreading  {     public static void main(String args[])     {       Sender sender = new Sender();       SenderWThreads sender1 = new SenderWThreads( “Hola ” , sender);  SenderWThreads sender2 =  new SenderWThreads( “Welcome to TutorAspire website “, sender);        // Start two threads of SenderWThreads type       sender1.start();       sender2.start();         // wait for threads to end       try      {         sender1.join();         sender2.join();       }       catch(Exception e)       {         System.out.println(“Interrupted”);       }     }   }  

Output:

Sending a Message: Hola   Hola Sent  Sending a Message: Welcome to TutorAspire website   Welcome to TutorAspire website Sent

Next TopicStatic Synchronization Example

Synchronized Block in Java

Synchronized Block in Java

Points to Remember

Syntax

Example of Synchronized Block

Synchronized Block Example Using Anonymous Class

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