synchronized的应用方式
- 代码块：作用范围在｛｝中，作用对象是调用这个代码块的对象。
- 方法：作用范围是一个方法，作用对象是调用这个方法的对象。
- 静态方法：作用范围是这个静态方法，作用对象是这个类的所有对象。
1，2是对象锁，3是类锁
举例
代码块
无this
public class SynchronizeDemo1 { static String syn = new String(); static class SynClass { public void myRun() { try { System.out.println(Thread.currentThread().getName() + "进来了"); synchronized (syn) { Thread.sleep(3000); } System.out.println(Thread.currentThread().getName() + "出来了"); } catch (InterruptedException e) { e.printStackTrace(); } } } static class Runnable1 implements Runnable { SynClass synClass; public Runnable1(SynClass synClass) { this.synClass = synClass; } @Override public void run() { synClass.myRun(); } } static class Runnable2 implements Runnable { SynClass synClass; public Runnable2(SynClass synClass) { this.synClass = synClass; } @Override public void run() { synClass.myRun(); } } public static void main(String[] args) { SynClass synClass = new SynClass(); Runnable1 runnable1 = new Runnable1(synClass); Runnable2 runnable2 = new Runnable2(synClass); Thread thread1 = new Thread(runnable1); thread1.setName("thread1"); Thread thread2 = new Thread(runnable2); thread2.setName("thread2"); thread1.start(); thread2.start(); }}运行的结果如下：
等thread1把代码块的执行完，释放了syn的锁，thread2才开始执行。
有this
public class SynchronizeDemo2 { static String syn = new String(); static class SynClass { public void myRun() { try { System.out.println(Thread.currentThread().getName() + "-myRun"); synchronized (this) { Thread.sleep(3000); } System.out.println(Thread.currentThread().getName() + "-myRun"); } catch (InterruptedException e) { e.printStackTrace(); } } public void myRun2() { try { System.out.println(Thread.currentThread().getName() + "-myRun2"); synchronized (this) { Thread.sleep(3000); } System.out.println(Thread.currentThread().getName() + "-myRun2"); } catch (InterruptedException e) { e.printStackTrace(); } } } static class Runnable1 implements Runnable { SynClass synClass; public Runnable1(SynClass synClass) { this.synClass = synClass; } @Override public void run() { synClass.myRun(); } } static class Runnable2 implements Runnable { SynClass synClass; public Runnable2(SynClass synClass) { this.synClass = synClass; } @Override public void run() { synClass.myRun2(); } } public static void main(String[] args) { SynClass synClass = new SynClass(); Runnable1 runnable1 = new Runnable1(synClass); Runnable2 runnable2 = new Runnable2(synClass); Thread thread1 = new Thread(runnable1); thread1.setName("thread1"); Thread thread2 = new Thread(runnable2); thread2.setName("thread2"); thread1.start(); thread2.start(); }}运行的结果如下：
等thread1把代码块的执行完，释放了this的锁，thread2才开始执行。
方法
public class SynchronizeDemo3 extends Thread { @Override public void run() { sync(); } synchronized public void sync(){ System.out.println(Thread.currentThread().getName() + "进来了"); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(Thread.currentThread().getName() + "出来了"); } public static void main(String[] args) { SynchronizeDemo3 synchronizeDemo1 = new SynchronizeDemo3(); Thread thread1 = new Thread(synchronizeDemo1); thread1.setName("thread1"); Thread thread2 = new Thread(synchronizeDemo1); thread2.setName("thread2"); thread1.start(); thread2.start(); }}运行的结果如下：
等thread1把方法执行完，释放了的锁，thread2才开始执行。
静态方法
public class SynchronizeDemo4 { static class Runnable1 implements Runnable { @Override public void run() { SynClass.myRun(); } } static class Runnable2 implements Runnable { @Override public void run() { SynClass.myRun2(); } } public static void main(String[] args) { Runnable1 runnable1 = new Runnable1(); Runnable2 runnable2 = new Runnable2(); Thread thread1 = new Thread(runnable1); thread1.setName("thread1"); Thread thread2 = new Thread(runnable2); thread2.setName("thread2"); thread1.start(); thread2.start(); }}class SynClass { public synchronized static void myRun() { System.out.println(Thread.currentThread().getName() + "-myRun"); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(Thread.currentThread().getName() + "-myRun"); } public synchronized static void myRun2() { System.out.println(Thread.currentThread().getName() + "-myRun2"); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(Thread.currentThread().getName() + "-myRun2"); }}运行的结果如下：
thread1等待thread2执行完才执行，说明是类锁
类所的另外一种形式
public class SynchronizeDemo5 { static class Runnable1 implements Runnable { @Override public void run() { synchronized (SynClass2.class){ System.out.println(Thread.currentThread().getName() + "-myRun"); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(Thread.currentThread().getName() + "-myRun"); } } } static class Runnable2 implements Runnable { @Override public void run() { synchronized (SynClass2.class){ System.out.println(Thread.currentThread().getName() + "-myRun2"); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(Thread.currentThread().getName() + "-myRun2"); } } } public static void main(String[] args) { Runnable1 runnable1 = new Runnable1(); Runnable2 runnable2 = new Runnable2(); Thread thread1 = new Thread(runnable1); thread1.setName("thread1"); Thread thread2 = new Thread(runnable2); thread2.setName("thread2"); thread1.start(); thread2.start(); }}class SynClass2 {}运行结果如下：