Cannot execute Synchronised thread

Question

I tried a code from Textbook about synchronized thread. Tried writing the code as it is. But getting the error:

cannot find symbol f.start(); and t.display();

The textbook code was supposed to be tried without the synchronized keyword. But it seems the compiler is unable to recognize the object. Please help..

class First 
{
    synchronized void display (String s)
    {
        System.out.println(s);

        try
        {
            Thread.sleep(1000);
        }
        catch(InterruptedException e)
        {
            System.out.println("Interrupted");  
        }
        System.out.println("***");
    }
}

class Second  implements Runnable 
{
    String s;
    First f;    
    Thread t;

    public Second(First f1,String s1)
    {
        f=f1;
        s=s1;
        t=new Thread(this);
        f.start();
    }

    public void run()
    {
        t.display(s);
    }
}

class SyncThread
{
    public static void main(String args[])
    {
        First f=new First();
        Second ob1=new Second(f,"First");
        Second ob2=new Second(f,"Second");
        Second ob3=new Second(f,"Third");

        try
        {
            ob1.t.join();
            ob2.t.join();
            ob3.t.join();
        }
        catch(InterruptedException e)
        {
            System.out.println("Interrupted");
        }
    }
}

Answer 1

Thread class does not have display method and your class First has the display method. I think you have wrongly typed t.display() and f.start(). Try to swith to f.display() and t.start().