用Lock对象来同步线程，实现生产者消费者模式

import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;public class DeadLock {public static void main(String[] args) {Account ac = new Account(4, "qhairen");new Thread(new Drawer(ac)).start();new Thread(new Depositer(ac)).start();new Thread(new Depositer(ac)).start();new Thread(new Depositer(ac)).start();}}class Account {private String name;private int total;private Lock lock = new ReentrantLock();public Account(int total, String name) {this.total = total;this.name = name;}public void draw() {lock.lock();try{while(total <= 0) {lock.unlock();try {Thread.sleep(10);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}lock.lock();}--total;System.out.println(name + " draw, now $" + total);try {Thread.sleep(100);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}} finally {lock.unlock();}}public void deposit() {lock.lock();try {while(total >= 5) {lock.unlock();try {Thread.sleep(10);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}lock.lock();}++total;System.out.println(name + " deposit, now $" + total);try {Thread.sleep(100);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}} finally {lock.unlock();}}}class Drawer implements Runnable {private Account ac;public Drawer(Account ac){this.ac = ac;}public void run() {while(true) {ac.draw();}}}class Depositer implements Runnable{private Account ac;public Depositer(Account ac){this.ac = ac;}public void run() {while(true) {ac.deposit();}}}

简述synchronized和java.util.concurrent.locks.Lock的异同 ？ 

主要相同点：Lock能完成synchronized所实现的所有功能 

主要不同点：Lock有比synchronized更精确的线程语义和更好的性能。synchronized会自动释放锁，而Lock一定要求程序员手工释放，并且必须在finally从句中释放。Lock还有更强大的功能，例如，它的tryLock方法可以非阻塞方式去拿锁。 

import java.util.concurrent.locks.Lock;

import java.util.concurrent.locks.ReentrantLock;

private Lock lock = new ReentrantLock();

lock.lock();

try{

  .......

} finally{

     lock.unlock();

}

ps：unlock()最好放在函数的最后，不然其他线程会得到锁，就可能不执行该线程剩下的代码了。