Java Reentrant getQueueLength()用法及代碼示例

ReentrantLock 類的 getQueueLength() 方法返回等待獲取鎖的線程數。該值是近似值，因為線程數可以在遍曆內部數據結構時動態更改。它用於監視狀態。

用法

public final int getQueueLength()

參數

沒有傳遞參數。

等待此鎖的估計線程數

拋出

不會拋出異常。

例子1

import java.util.concurrent.locks.ReentrantLock;
 
 public class ReentrantLockgetQueueLengthExample1  {
     public static void main(String[] args) {
  
            ReentrantLock lock=new ReentrantLock();
            MyRunnableClass90 myRnbl=new MyRunnableClass90(lock);
            new Thread(myRnbl,"Thread-1").start();
                        
     }
 }
    
 class MyRunnableClass90 implements Runnable{
     
     ReentrantLock lock;
     public MyRunnableClass90(ReentrantLock lock) { 
            this.lock=lock;
     }
     
     public void run(){
            int i;
            Thread t1 = new Thread();
            Thread t2 = new Thread();
            t1.holdsLock(t1);
            t2.holdsLock(t2);
    	 for(i=5;i<=10;i++) {
    		 if(i==7)
    		 {
            System.out.println(" getQueueLength = "+lock.getQueueLength()+"  ");
    		 }
    		 if(i==5)
           System.out.println(Thread.currentThread().getName()
                         +" has released the lock.");
            
           
    	 }
     }
 }

輸出：

Thread-1 has released the lock.
 getQueueLength = 0

例子2

import java.util.concurrent.locks.ReentrantLock;
 
 public class ReentrantLockgetQueueLengthExample2 {
     public static void main(String[] args) {
  
            ReentrantLock lock=new ReentrantLock();
            MyRunnableClass10 myRnbl=new MyRunnableClass10(lock);
            new Thread(myRnbl,"ThreadA").start();
            new Thread(myRnbl,"ThreadB").start();
            new Thread(myRnbl,"ThreadC").start();
            
     }
 }
   
  class MyRunnableClass10 implements Runnable{
     
     ReentrantLock lock;
     public MyRunnableClass10(ReentrantLock lock) { 
            this.lock=lock;
     }
     
     public void run(){
            
           
            lock.lock();
  
            System.out.println(Thread.currentThread().getName()
                         +" has got the  lock.");
            
                   try {
					Thread.sleep(2000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
           
            System.out.println("getQueueLength = "+lock.getQueueLength());
            
            lock.unlock();  
     }
 }

輸出：

ThreadB has got the  lock.
getQueueLength = 2
ThreadA has got the  lock.
getQueueLength = 1
ThreadC has got the  lock.
getQueueLength = 0

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注：本文由純淨天空篩選整理自 Java Reentrant getQueueLength() Method。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。