synchronized java

1synchronized blocks the next thread's call to method 
2 as long as the previous thread's execution is not finished. 
3  Threads can access this method one at a time. 
4  Without synchronized all threads can access this method simultaneously.

1The synchronized keyword is all about different threads reading and writing 
2to the same variables, objects and resources.

1public class MyCounter {
2
3  private int count = 0;
4
5  public synchronized void add(int value){
6      this.count += value;
7  }
8}
9

1class First
2{
3  synchronized public void display(String msg)
4  {
5    System.out.print ("["+msg);
6    try
7    {
8      Thread.sleep(1000);
9    }
10    catch(InterruptedException e)
11    {
12      e.printStackTrace();
13    }
14    System.out.println ("]");
15  }
16}
17
18class Second extends Thread
19{
20  String msg;
21  First fobj;
22  Second (First fp,String str)
23  {
24    fobj = fp;
25    msg = str;
26    start();
27  }
28  public void run()
29  {
30    fobj.display(msg);
31  }
32}
33
34public class MyThread
35{
36  public static void main (String[] args)
37  {
38    First fnew = new First();
39    Second ss = new Second(fnew, "welcome");
40    Second ss1= new Second(fnew,"new");
41    Second ss2 = new Second(fnew, "programmer");
42  }
43}
44