Java Programming - Java.lang Class - Discussion

public class Test 
{ 
    public static void main(String[] args) 
    {
        final StringBuffer a = new StringBuffer(); 
        final StringBuffer b = new StringBuffer(); 

        new Thread() 
        { 
            public void run() 
            {
                System.out.print(a.append("A")); 
                synchronized(b) 
                { 
                    System.out.print(b.append("B")); 
                } 
            } 
        }.start(); 
            
        new Thread() 
        {
            public void run() 
            {
                System.out.print(b.append("C")); 
                synchronized(a) 
                {
                    System.out.print(a.append("D")); 
                } 
            } 
        }.start(); 
    } 
}