java线程synchronized与死锁

对象锁：每个对象有一把锁，若对象的属性和函数被synchronized修饰的，则他们在被访问之前必须获得对象的锁。

类锁：每个类有一把锁，若类静态的属性和函数被synchronized修饰的，则他们在被访问之前必须获得对象的锁。

如果被synchronized修饰的函数，调用同一个对象或类被synchronized修饰的函数或属性时，会发生死锁。

 

 

package com.threadPool;

import java.util.LinkedList;
import java.util.logging.Logger;

public class TestPool {
	private final static int  nThreads = 100;
    private final static Mythread[] threads = new Mythread[nThreads];
    private final static LinkedList queue = new LinkedList();
    public TestPool(int nThreads)
    {
        PoolWorker poolWorker1 = new PoolWorker();
        poolWorker1.setName("poolwork1");
        poolWorker1.start();
        PoolWorker poolWorker2 = new PoolWorker();
        poolWorker2.setName("poolwork2");
        poolWorker2.start();
        
        for (int i=0; i<nThreads; i++) {
            threads[i] = new Mythread();
            threads[i].setName("test "+i);
//            execute(threads[i]);
            /*try {
				Thread.sleep(10000);
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}*/
            
//            threads[i].start();
        }
    }
    
    private static void start(){
    int i=100;
    while (i-- >0) {
		execute(threads[i]);
		/*try {
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}*/
	}
    }
    public static void execute(Runnable r) {
        synchronized(queue) {
            queue.addLast(r);
            queue.notify();
        }
    }
    private class PoolWorker extends Thread {
        public void run() {
            Runnable r;
            while (true) {
                synchronized(queue) {
                    while (queue.isEmpty()) {
                        try
                        {
                        	System.out.print("pool work thread "+getName()+" wait \n");
                            queue.wait();
                        }
                        catch (InterruptedException ignored)
                        {
                        }
                    }
                    r = (Runnable) queue.removeFirst();
                }
                // If we don't catch RuntimeException, 
                // the pool could leak threads
                try {
                	System.out.print("pool work "+getName()+" and task is "+r.toString()+"\n");
                	
                    r.run();
                }
                catch (RuntimeException e) {
                    // You might want to log something here
                }
            }
        }
    }
    
    private class Mythread extends Thread{

		/* (non-Javadoc)
		 * @see java.lang.Thread#run()
		 */
		@Override
		public void run() {
			// TODO Auto-generated method stub
//			super.run();
			System.out.print("the"+getName()+"\n");
		}
    	
    }
    
    public static void  main(String[] aString){
    	TestPool testPool = new TestPool(100);
    	start();
    }
}

 这是一段简单的线程池的实例： 所有的用户任务放到queue队列中，线程池中有2个常驻工作线程，当queue中有任务时，工作线程就被唤醒，否则工作线程就进入等待状态。