Example of thread deadlock, uncomment the counter to see interleaving then uncomment the synchronised statements to see deadlock

Deadlock.java

class Friend {
        
String name;
        
public Friend(String name) {
          this.name = name;
      }
     
      public /* synchronized */ void waveAt(Friend f) {
          System.out.println(name + " waves...");
          int a=0;
          //for (int i =0;i<10000000;i++) {
          //    a++;
          // }
          f.waveBack();
      }
      public /* synchronized */  void waveBack() {
           System.out.println(name + " waves back.");
      }
}

class greet extends Thread
{
      
      Friend  one,two;
      
      greet(Friend f, Friend g)
      {
        one=f; 
        two=g;
      }

      public void run() { 
        one.waveAt(two);
      }

}


public class Deadlock {
   
    public static void main(String[] args) {
        Friend fred = new Friend("Alice");
        Friend jack = new Friend("Bob");
        
          new greet(fred,jack).start();
          new greet(jack,fred).start();
      

    }
}