Simple Example of Java program about Lock Contention and Solution to Fix

 

Lock Contention Program

class Table {
    
    void printTable(int n)
    {
        for (int i=0; i<10; i++)
        {
            System.out.println(n*i);
           
            try
            {
                Thread.sleep(2000);
            }
            catch(Exception e)
            {
                System.out.println(e);
            }
        }
    }
}

class MyThread1 extends Thread {
       Table table;
       public MyThread1(Table table)
       {
           this.table = table;
       }
      
       @Override
       public void run()
       {
           table.printTable(5);
       }
      
}

class MyThread2 extends Thread {
       Table table;
       public MyThread2(Table table)
       {
           this.table = table;
       }
      
       @Override
       public void run()
       {
           table.printTable(10);
       }
      
}

public class Test {
    public static void main(String[] args) {
         
        Table obj = new Table();
        MyThread1 t1 = new MyThread1(obj);
        MyThread2 t2 = new MyThread2(obj);
        t1.start();
        t2.start();
    }
  }

The problem with this code is that both threads are accessing the shared Table object at the same time, and thus may be interfering with each other's output. One possible solution is to use synchronization to ensure that only one thread can access the printTable method at a time. Here's an example of how to modify the code to use synchronization

class Table {
    
    synchronized void printTable(int n)
    {
        for (int i=0; i<10; i++)
        {
            System.out.println(n*i);
            
            try
            {
                Thread.sleep(2000);
            }
            catch(Exception e)
            {
                System.out.println(e);
            }
        }
    }
}

class MyThread1 extends Thread {
       Table table;
       public MyThread1(Table table)
       {
           this.table = table;
       }
       
       @Override
       public void run()
       {
           table.printTable(5);
       }
       
}

class MyThread2 extends Thread {
       Table table;
       public MyThread2(Table table)
       {
           this.table = table;
       }
       
       @Override
       public void run()
       {
           table.printTable(10);
       }
       
}

public class Test {
    public static void main(String[] args) {
          
        Table obj = new Table();
        MyThread1 t1 = new MyThread1(obj);
        MyThread2 t2 = new MyThread2(obj);
        t1.start();
        t2.start();
    }
}
 

In this modified code, the printTable method is declared with the synchronized keyword, which means that only one thread can execute it at a time. This ensures that the output of the multiplication tables will not be interleaved or otherwise interfered with.

 
 
 

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About Ashadullah Shawon

I am Ashadullah Shawon. I am a Software Engineer. I studied Computer Science and Engineering (CSE) at RUET. I Like To Share Knowledge. Learn More: Click Here