本篇主要介绍synchronized静态方法和synchronized(class)的使用
1,静态同步方法的锁对象是class不同于静态同步方法的锁对象是类实例
package chapter2.synTwoLock;
/*
演示静态方法锁对象和非静态方法锁对象不是同一个锁,
从结果来看ac是异步的,a,b是同步的,因为printa和printb都是静态同步方法,二者锁对象都是class
而printC是非静态的同步方法,锁对象是类实例,和a,b不是一个对象监视器,是异步调用的
线程名称为:a 在 1525529667507 进入printA
线程名称为:c 在 1525529667509 进入printC
线程名称为:c 在 1525529667509 离开printC
线程名称为:a 在 1525529670508 离开printA
线程名称为:b 在 1525529670509 进入printB
线程名称为:b 在 1525529670509 离开printB
*/
public class Run {
public static void main(String[] args) {
Service service=new Service();
ThreadA ta=new ThreadA(service);
ta.setName("a");
ta.start();
ThreadB tb=new ThreadB(service);
tb.setName("b");
tb.start();
ThreadC tc=new ThreadC(service);
tc.setName("c");
tc.start();
}
}
package chapter2.synTwoLock;
public class Service {
synchronized public static void printA() {
try {
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 进入printA");
Thread.sleep(3000);
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 离开printA");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
synchronized public static void printB() {
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 进入printB");
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 离开printB");
}
synchronized public void printC() {
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 进入printC");
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 离开printC");
}
}
package chapter2.synTwoLock;
public class ThreadA extends Thread {
private Service service;
public ThreadA(Service service) {
super();
this.service=service;
}
@Override
public void run() {
super.run();
service.printA();
}
}
package chapter2.synTwoLock;
public class ThreadB extends Thread {
private Service service;
public ThreadB(Service service) {
super();
this.service=service;
}
@Override
public void run() {
super.run();
service.printB();
}
}
package chapter2.synTwoLock;
public class ThreadC extends Thread {
private Service service;
public ThreadC(Service service) {
super();
this.service=service;
}
@Override
public void run() {
super.run();
service.printC();
}
}
2,Class锁可以对类的所有实例起作用
package chapter2.synMoreObjectStaticOneLock;
/*演示静态同步方法,对不同类实例的同步效果,也就是Class锁可以对类的所有实例起作用
* a,b线程的service实例是两个不同的对象,但结果是b线程等待a线程结束才会进入静态同步方法,
* 如果是非静态的同步方法,不同实例的调用是异步的,这里注意区分
线程名称为:a 在 1525529960193 进入printA
线程名称为:a 在 1525529963193 离开printA //这里等待3s
线程名称为:b 在 1525529963193 进入printB
线程名称为:b 在 1525529963193 离开printB
*/
public class Run {
public static void main(String[] args) {
Service service1=new Service();
Service service2=new Service();
ThreadA ta=new ThreadA(service1);
ta.setName("a");
ta.start();
ThreadB tb=new ThreadB(service2);
tb.setName("b");
tb.start();
}
}
package chapter2.synMoreObjectStaticOneLock;
public class Service {
synchronized public static void printA() {
try {
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 进入printA");
Thread.sleep(3000);
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 离开printA");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
synchronized public static void printB() {
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 进入printB");
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 离开printB");
}
}
package chapter2.synMoreObjectStaticOneLock;
public class ThreadA extends Thread {
private Service service;
public ThreadA(Service service) {
super();
this.service=service;
}
@Override
public void run() {
super.run();
service.printA();
}
}
package chapter2.synMoreObjectStaticOneLock;
public class ThreadB extends Thread {
private Service service;
public ThreadB(Service service) {
super();
this.service=service;
}
@Override
public void run() {
super.run();
service.printB();
}
}
3,synchronized(class)
静态方法的synchronized(class)代码块和静态同步方法效果相同package chapter2.synBlockMoreObjectOneLock;
public class Service {
public static void printA() {
synchronized (Service.class) {
try {
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 进入printA");
Thread.sleep(3000);
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 离开printA");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public static void printB() {
synchronized (Service.class) {
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 进入printB");
System.out.println(
"线程名称为:" + Thread.currentThread().getName() + " 在 " + System.currentTimeMillis() + " 离开printB");
}
}
}
package chapter2.synBlockMoreObjectOneLock;
/*演示静态方法的synchronized(class)代码块和静态同步方法效果相同
线程名称为:a 在 1525530881142 进入printA
线程名称为:a 在 1525530884143 离开printA
线程名称为:b 在 1525530884143 进入printB
线程名称为:b 在 1525530884144 离开printB
*/
public class Run {
public static void main(String[] args) {
Service service1=new Service();
Service service2=new Service();
ThreadA ta=new ThreadA(service1);
ta.setName("a");
ta.start();
ThreadB tb=new ThreadB(service2);
tb.setName("b");
tb.start();
}
}
package chapter2.synBlockMoreObjectOneLock;
public class ThreadA extends Thread {
private Service service;
public ThreadA(Service service) {
super();
this.service=service;
}
@Override
public void run() {
super.run();
service.printA();
}
}
package chapter2.synBlockMoreObjectOneLock;
public class ThreadB extends Thread {
private Service service;
public ThreadB(Service service) {
super();
this.service=service;
}
@Override
public void run() {
super.run();
service.printB();
}
}
参考:<java多线程编程核心技术>