- 对象上有关键字
package com.study.juc.sync;
import java.util.concurrent.TimeUnit;
public class Test1 {
public static void main(String[] args) throws InterruptedException {
Phone phone = new Phone();
Thread t1= new Thread(()->{
try {
phone.sendSms();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
},"A");
t1.start();
TimeUnit.SECONDS.sleep(1);
Thread t2=new Thread(()->{
phone.call();
},"B");
t2.start();
Thread t3=new Thread(()->{
phone.hello();
},"c");
t3.start();
}
}
class Phone{
public synchronized void call(){
System.out.println("打电话");
}
public synchronized void sendSms() throws InterruptedException {
TimeUnit.SECONDS.sleep(4);
System.out.println("发短信");
}
public void hello(){
System.out.println("hello ");
}
}
请输出上面例子的结果。
- 结论
如果时同一个对象上，加 synchronized 那么这个对象的一个方法先进入，另外的方法只能等待，需要登台获取锁的对象完成才能执行。
如果方法上没有锁，那么不会等待。
- 两个对象的调用
package com.study.juc.sync;
import java.util.concurrent.TimeUnit;
public class Test2 {
public static void main(String[] args) throws InterruptedException {
Phone2 phone1 = new Phone2();
Phone2 phone2 = new Phone2();
Thread t1= new Thread(()->{
try {
phone1.sendSms();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
},"A");
t1.start();
TimeUnit.SECONDS.sleep(1);
Thread t2=new Thread(()->{
phone2.call();
},"B");
t2.start();
}
}
class Phone2{
public synchronized void call(){
System.out.println("打电话");
}
public synchronized void sendSms() throws InterruptedException {
TimeUnit.SECONDS.sleep(4);
System.out.println("发短信");
}
public void hello(){
System.out.println("hello ");
}
}
创建两个对象，分别调用其方法，由于是两个对象，锁的作用范围也是对象，因此两个对象的锁不互相干扰。
- 静态方法
package com.study.juc.sync;
import java.util.concurrent.TimeUnit;
public class Test3 {
public static void main(String[] args) throws InterruptedException {
Phone3 phone1 = new Phone3();
Phone3 phone2 = new Phone3();
Thread t1= new Thread(()->{
try {
phone1.sendSms();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
},"A");
t1.start();
TimeUnit.SECONDS.sleep(1);
Thread t2=new Thread(()->{
phone2.call();
},"B");
t2.start();
}
}
class Phone3{
public static synchronized void call(){
System.out.println("打电话");
}
public static synchronized void sendSms() throws InterruptedException {
TimeUnit.SECONDS.sleep(4);
System.out.println("发短信");
}
}
synchronized 作用在 class 上，所以锁的对象是 class。
- 一个实例方法，一个类方法
package com.study.juc.sync;
import java.util.concurrent.TimeUnit;
public class Test4 {
public static void main(String[] args) throws InterruptedException {
Phone4 phone = new Phone4();
Thread t1= new Thread(()->{
try {
phone.sendSms();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
},"A");
t1.start();
TimeUnit.SECONDS.sleep(1);
Thread t2=new Thread(()->{
phone.call();
},"B");
t2.start();
}
}
class Phone4{
public synchronized void call(){
System.out.println("打电话");
}
public static synchronized void sendSms() throws InterruptedException {
TimeUnit.SECONDS.sleep(4);
System.out.println("发短信");
}
}
一个调用静态方法，一个调用实例方法，实际是两把锁相互不影响。
