java 多線程操作同一個變數

 例子，假設是個賣票系統，多個線程（例子中有2個線程）操作同一個變數ticketCount（餘票的數量）。

Expected : 多個線程對同個變數會同步操作，不會造成混亂。

 

public class Test implements Runnable {

 private String threadName;
 private int ticketCount;

 public Test(String threadName, int ticketCount) {
  this.threadName = threadName;
  this.ticketCount = ticketCount;
 }

 public synchronized int sellTicket() {
  return ticketCount--;
 }

 @Override
 public void run() {
  // TODO Auto-generated method stub
  while (ticketCount > 0) {
   System.out.println(getThreadName() + " : " + sellTicket());
  }
 }

 public String getThreadName() {
  Thread a = Thread.currentThread();
  return a.getName();
 }

 public static void main(String[] args) {
  Test t1 = new Test("Ticket available ", 10);
  Thread thread1 = new Thread(t1,
    "1 window sell ticket ,ticket available ");
  Thread thread2 = new Thread(t1,
    "2 window sell ticket ,ticket available ");
  thread1.start();
  thread2.start();
 }

}

 

----------------------列印結果（每次運行不一樣）----------------------

2 window sell ticket ,ticket available  : 9
2 window sell ticket ,ticket available  : 8
2 window sell ticket ,ticket available  : 7
2 window sell ticket ,ticket available  : 6
2 window sell ticket ,ticket available  : 5
2 window sell ticket ,ticket available  : 4
1 window sell ticket ,ticket available  : 10
2 window sell ticket ,ticket available  : 3
1 window sell ticket ,ticket available  : 2
2 window sell ticket ,ticket available  : 1