线程的生命周期
线程锁的作用范围:
1、对象实例锁,锁住同一个对象
demo1:
当t1获取线程时,t2会等待t1睡两秒后执行,这也说明了Thread.sleep()不会释放锁资源
/** * 锁的作用范围 */ public class SynchronizedTest { public static void main(String[] args) { SynchronizedTest synchronizedTest = new SynchronizedTest(); new Thread(()->{ synchronizedTest.test1(); },"t1").start(); new Thread(()->{ synchronizedTest.test1(); },"t2").start(); } synchronized void test1(){ System.out.println(Thread.currentThread().getName()+"获取锁"); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } }
demo2:当我们再new一个SynchronizedTest 时,synchronizedTest ,synchronizedTest2 是不同的实例,t1,t2线程几乎是同时输出结果,这也说明了
synchronized 修饰实例方法时,锁住得是实例对象,相当于synchronized(this) void test1(){
public class SynchronizedTest { public static void main(String[] args) { SynchronizedTest synchronizedTest = new SynchronizedTest(); SynchronizedTest synchronizedTest2 = new SynchronizedTest(); new Thread(()->{ synchronizedTest.test1(); },"t1").start(); new Thread(()->{ synchronizedTest2.test1(); },"t2").start(); } synchronized void test1(){ System.out.println(Thread.currentThread().getName()+"获取锁"); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } }
demo3:synchronized这次修饰代码块,其执行结果是和demo1是一样的,这三种都是锁住的对象实例
public class SynchronizedTest { public static void main(String[] args) { SynchronizedTest synchronizedTest = new SynchronizedTest(); new Thread(()->{ synchronizedTest.test1(); },"t1").start(); new Thread(()->{ synchronizedTest.test1(); },"t2").start(); } void test1(){ synchronized(this){ System.out.println(Thread.currentThread().getName()+"获取锁"); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } } }
2、静态方法,类对象:锁住的是Class,类锁
demo4:当t1获取线程时,t2会等待t1睡两秒后执行,这里的静态方法锁住的是类对象
public class SynchronizedTest { public static void main(String[] args) { new Thread(()->{ SynchronizedTest.test1(); },"t1").start(); new Thread(()->{ SynchronizedTest.test1(); },"t2").start(); } synchronized static void test1(){ System.out.println(Thread.currentThread().getName()+"获取锁"); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } }
demo5:当我们new了两个不同的实例,当t1线程获取锁是,t2线程会等待两秒后执行,这说明了锁住了类对象,
synchronizedTest,synchronizedTest2 是两个不同的实例,当是同一个类对象。
public class SynchronizedTest { public static void main(String[] args) { SynchronizedTest synchronizedTest = new SynchronizedTest(); SynchronizedTest synchronizedTest2 = new SynchronizedTest(); new Thread(()->{ synchronizedTest.test1(); },"t1").start(); new Thread(()->{ synchronizedTest2.test1(); },"t2").start(); } void test1(){ synchronized (SynchronizedTest.class) { System.out.println(Thread.currentThread().getName() + "获取锁"); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } } }