如下代碼所示，為什么繼承了Thread的線程使用同步方法的時(shí)候無(wú)法鎖住呢？而使用同步代碼塊就沒(méi)有問(wèn)題package leetcode; import javax.swing.plaf.synth.SynthSeparatorUI; import com.sun.org.apache.xerces.internal.util.SynchronizedSymbolTable; public class mainEntry {     public static void main(String[] agrs)     {         // 創(chuàng)建 3 個(gè)窗口         TicketSell t1 = new TicketSell("A窗口");         TicketSell t2 = new TicketSell("B窗口");         TicketSell t3 = new TicketSell("C窗口");         // 啟動(dòng) 3 個(gè)窗口進(jìn)行買票         t1.start();         t2.start();         t3.start();     } } class TicketSell extends Thread {     private static int num = 50;     public TicketSell(String name)     {         super(name);     }     @Override     public void run()     {         for(int i = 0;i<50;i++)             sell();     }     public synchronized void sell() {         if (num > 0)         {             try             {                 // 模擬賣一次票所需時(shí)間                 Thread.sleep(10);             } catch (InterruptedException e)             {                 e.printStackTrace();             }             System.out.println(this.currentThread().getName() + "賣出一張票，剩余" + (--num) + "張");         }     } }這是輸出....A窗口賣出一張票，剩余2張C窗口賣出一張票，剩余1張B窗口賣出一張票，剩余0張A窗口賣出一張票，剩余-1張