Java多线程06_重入锁ReentrantLock

叁歲伎倆 2022-12-03 13:18 167阅读 0赞

**Java多线程06\_重入锁ReentrantLock**

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public class TestLock { 
    	public static void main(String[] args) { 
    		TestLock2 testLock2 = new TestLock2();
    		new Thread(testLock2).start();
    		new Thread(testLock2).start();
    		new Thread(testLock2).start();
    
    	}
    }
    
    class TestLock2 implements Runnable { 
    
    	int ticketNums = 10;
    
    	@Override
    	public void run() { 
    		while (true) { 
    			if (ticketNums > 0) { 
    				try { 
    					Thread.sleep(1000);
    				} catch (InterruptedException e) { 
    					e.printStackTrace();
    				}
    				System.out.println(ticketNums--);
    			} else { 
    				break;
    			}
    
    		}
    	}
    
    }

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import java.util.concurrent.locks.ReentrantLock;
     
    public class TestLock { 
    	public static void main(String[] args) { 
    		TestLock2 testLock2 = new TestLock2();
    		new Thread(testLock2).start();
    		new Thread(testLock2).start();
    		new Thread(testLock2).start();
    		
    	}
    }
    
    class TestLock2 implements Runnable{ 
    
    	int ticketNums = 10;
    	
    	private final ReentrantLock lock = new ReentrantLock();
    	
    	@Override
    	public void run() { 
    		while(true) { 
    			lock.lock();
    			try { 
    				if(ticketNums>0) { 
    					try { 
    						Thread.sleep(1000);
    					} catch (InterruptedException e) { 
    						e.printStackTrace();
    					}
    					System.out.println(ticketNums--);
    				}else { 
    					break;
    				}
    			}  finally { 
    				lock.unlock();
    					
    		}
    	}
    	
    }

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**synchronized 与 Lock 的对比：**

Lock是显示锁（手动开启和关闭锁，别忘记关闭锁）
    synchronized 是隐式锁，出了作用域自动释放
    
    Lock只有代码块锁
     synchronized有代码块锁和方法锁
    
    使用 Lock 锁，JVM 将花费较少时间来调度线程，性能更好，并且具有更好的扩展性（提供更多的子类，比如 ReentrantLock）