java中的同步 - new ReentrantLock（true）和new ReentrantLock（false）產生相同的結果？

Question

ReentrantLock在創建Lock對象時提供了boolean fair標誌。

1. fair：true

   線程提供獲得基礎上，他們一直在等待的時間臨界區。

2. fair：false

   有給了臨界區的線程沒有具體政策。

下面是我爲同一代碼：

public class ThreadDemo { 
    private Lock lock = new ReentrantLock(false); 

    public static void main(String[] args) { 
     ThreadDemo td = new ThreadDemo(); 
     Thread[] tArr = new Thread[5]; 
     // Creates 5 thread and stores them in a array 
     for (int i = 0; i < 5; i++) { 
      tArr[i] = new Thread(() -> { 
       td.enterCriticalSection(new Date().getTime()); 
      }, "Thread " + i); 
     } 
     // Iterate through the array and start it. 
     for (int i = 0; i < 5; i++) { 
      tArr[i].start(); 
      try { 
       Thread.currentThread().sleep(1000); 
      } catch (InterruptedException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 

     } 
    } 

    public void enterCriticalSection(long waitTime) { 
     System.out.println(Thread.currentThread().getName() + " requesting critical section at:" 
       + new SimpleDateFormat("HH:mm:ss:SSS").format(new Date().getTime())); 
     // Gets Lock 
     lock.lock(); 

     try { 
      /* 
      * Logs the entry time in critical section and waiting period for 
      * the thread 
      */ 
      System.out.println(Thread.currentThread().getName() + " in critical section at " 
        + new SimpleDateFormat("HH:mm:ss:SSS").format(new Date().getTime())); 
      Thread.currentThread().sleep(5000); 
     } catch (InterruptedException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } finally { 
      // Releases lock 
      lock.unlock(); 
     } 

     } 
} 

但不管公平爲真和公平假我得到相同的結果，即線程這等待最長時間得到關鍵部分

Thread 0 requesting critical section at:01:57:48:562 
Thread 0 in critical section at 01:57:48:563 
Thread 1 requesting critical section at:01:57:49:520 
Thread 2 requesting critical section at:01:57:50:520 
Thread 3 requesting critical section at:01:57:51:520 
Thread 4 requesting critical section at:01:57:52:520 
Thread 1 in critical section at 01:57:53:564 
Thread 2 in critical section at 01:57:58:564 
Thread 3 in critical section at 01:58:03:565 
Thread 4 in critical section at 01:58:08:566 

Answer 1

全部fair false的意思是說，鎖會讓線程在它想要的。有了少量的線程，它可能恰好是他們一直在等待的順序，但它不能保證這一點。