/** * mark_ * 1: 类锁,对象锁 * 2: 对象锁:实例的实例同步方法只能被同一个线程进入;(类的同步方法也是如此) **/public class ObjectLockMdTest {    public synchronized void m1() throws Exception {        System.err.println("m1:enter");        while (true) {            Thread.sleep(10000);//10秒            break;        }        System.err.println("m1:end");    }    public synchronized void m2() {        System.err.println("m2");    }    public static synchronized void m3() throws Exception {        System.err.println("m3:enter");        while (true) {            Thread.sleep(10000);//10秒            break;        }        System.err.println("m3:end");    }    public static synchronized void m4() {        System.err.println("m4");    }    public static void testObjectLock() {        ObjectLockMdTest test = new ObjectLockMdTest();        Thread t1 = new Thread(new Runnable() {            @Override            public void run() {                try {                    test.m1();                } catch (Exception e) {                    e.printStackTrace();                }            }        });        Thread t2 = new Thread(new Runnable() {            @Override            public void run() {                test.m2();            }        });        t1.start();        t2.start();    }    public static void testClassLock() {        Thread t3 = new Thread(new Runnable() {            @Override            public void run() {                try {                    ObjectLockMdTest.m3();                } catch (Exception e) {                    e.printStackTrace();                }            }        });        Thread t4 = new Thread(new Runnable() {            @Override            public void run() {                ObjectLockMdTest.m4();            }        });        t3.start();        t4.start();    }    public static void main(String[] args) throws Exception {       // testObjectLock();        testClassLock();    }}