JAVA_Thread_deadlock

package com.kk.thread;
/*
 *  
 *  , :int b;synchronized(b)
 */
public class TicketsSystem {

    public static void main(String[] args)throws Exception {
        SellThread sell=new SellThread();
        new Thread(sell).start();
        Thread.sleep(1);// thread1 , b=false;
        sell.b=true;
        new Thread(sell).start();
    }

}

class SellThread implements Runnable{

    int tickets=1000;
    Object obj=new Object();
    boolean b=false;
    public void run() {
                if (b) {
                    sell();
                }else{
                    synchronized(obj){ // obj 
                        while(true){
                            if (tickets>0) {
                                try {
                                    Thread.currentThread().sleep(10);
                                } catch (InterruptedException e) {
                                    e.printStackTrace();
                                }
                                synchronized(this){ // , this sell 
                                    System.out.println("obj___"+Thread.currentThread().getName()+"__"+tickets);
                                    tickets--;
                                }
                            }
                        }
                    }
                }
    }
    
    /*
     *  (this)
     *  (Class)
     */
    private synchronized void sell(){ // （this）
        while(true){
            if (tickets>0) {
                try {
                    Thread.currentThread().sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                synchronized(obj){ // ,obj run synchronized(obj) 
                    System.out.println("this___"+Thread.currentThread().getName()+"__"+tickets);
                    tickets--;
                }
            }
        }
    }
    
}