死锁的演示
import java.util.concurrent.TimeUnit;import java.util.concurrent.locks.ReentrantLock;/** * 第一个线程获取local锁后，偿试获取other锁，如果失败，则等待5秒重试 * 同样第二个线程获取other锁后，偿试获取local锁，如果失败，则放弃等待5秒重试 * User: sunlong * Date: 13-10-18 * Time: 下午5:10 */public class DeadLock { public static void main(String[] args){ final Update a = new Update("this is a"); final Update b = new Update("this is b"); final App2 local = new App2("app1"); final App2 other = new App2("app2"); new Thread(new Runnable() { @Override public void run() { local.update(a, other); } }).start(); new Thread(new Runnable() { @Override public void run() { other.update(b, local); } }).start(); }}class Update{ private String text; public Update(String text){ this.text = text; } public String getText(){ return this.text; }}/** * 这个是传统的syschronized方式演示死锁 */class App{ private final String indent; public App(String indent){ this.indent = indent; } public synchronized void update(Update update, App backup){ System.out.println(indent + ": recvd:" + update.getText() + "; backup:" + backup.getIndent()); /*try{ TimeUnit.SECONDS.sleep(5); }catch (Exception e){ }*/ backup.confirmUpdate(this, update); } private synchronized void confirmUpdate(App backup, Update update){ System.out.println(indent + ": recvd:" + update.getText() + "; backup:" + backup.getIndent()); } String getIndent() { return indent; }}/** * 用lock重写 */class App2{ private final String indent; private final ReentrantLock lock = new ReentrantLock(); public App2(String indent){ this.indent = indent; } public void update(Update update, App2 backup){ boolean acquired = false; boolean done = false; while (!done){ System.out.println("--------------------------------"); try { acquired = lock.tryLock(5, TimeUnit.MILLISECONDS); if(acquired){ System.out.println(indent + ": recvd:" + update.getText() + "; backup:" + backup.getIndent()); done = backup.confirmUpdate(this, update); } } catch (InterruptedException e) { e.printStackTrace(); } finally { if(acquired){ lock.unlock(); } } if(!done){ try { TimeUnit.SECONDS.sleep(5); } catch (InterruptedException e) { e.printStackTrace(); } } } } private boolean confirmUpdate(App2 backup, Update update){ boolean acquired = false; try{ acquired = lock.tryLock(5, TimeUnit.MILLISECONDS); if(acquired){ System.out.println(indent + ": recvd confirmed:" + update.getText() + "; backup:" + backup.getIndent()); return true; } } catch (InterruptedException e) { e.printStackTrace(); } finally { if(acquired){ lock.unlock(); } } return false; } String getIndent() { return indent; }}?