synchronized 与 static synchronized 的区别：
synchronized ：锁住的只能锁住一个对象就是当前对象
static synchronized ：锁住的是类，所有对象都会锁住
下面demo实例展示。
1. synchronized的demo
synchronized 锁住的是对象，只锁当前实例。
代码：Demo类和Dog类
Dog类
package com.fanjia.demo_fanjia.test;
/**
* @author fanjia
* @description TODO
* @date 2021/7/29 13:17
*/
public class Dog {
//第一次没有加static 则 1和2 会同时打印
//因为synchronized锁住的是对象，所以这里的sleep不会影响2的打印
public synchronized void eat(int name) throws InterruptedException {
System.out.println("you are dog"+name);
System.out.println();
Thread.sleep(10000);
}
}
Demo类
new 两个对象，则会同时打印说明 synchronized 锁不住不同对象的实例
package com.fanjia.demo_fanjia.test;
import jdk.nashorn.internal.objects.annotations.Where;
/**
* @author fanjia
* @description TODO
* @date 2021/7/29 13:18
*/
public class Demo {
public static void main(String[] args) {
Dog dog1 = new Dog();
Dog dog2 = new Dog();
new Thread(new Runnable() {
@Override
public void run() {
while(true){
try {
dog1.eat(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
while(true){
try {
dog2.eat(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
}
}
打印结果
you are dog1
you are dog2
==============================================
2.static synchronized
static synchronized 锁住的是 类，全部对象都会被锁住
demo类和Dog类
Dog类
package com.fanjia.demo_fanjia.test;
/**
* @author fanjia
* @description TODO
* @date 2021/7/29 13:17
*/
public class Dog {
//第二次加上static 则 1会先打印， 间隔 10秒， 再打印2
//因为static synchronized锁住的是类，所有对象，所以这里的sleep会影响2的打印
public static synchronized void eat(int name) throws InterruptedException {
System.out.println("you are dog"+name);
System.out.println();
Thread.sleep(10000);
}
}
Demo类
package com.fanjia.demo_fanjia.test;
import jdk.nashorn.internal.objects.annotations.Where;
/**
* @author fanjia
* @description TODO
* @date 2021/7/29 13:18
*/
public class Demo {
public static void main(String[] args) {
Dog dog1 = new Dog();
Dog dog2 = new Dog();
new Thread(new Runnable() {
@Override
public void run() {
while(true){
try {
dog1.eat(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
while(true){
try {
dog2.eat(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
}
}
打印结果
2还没打印出来，会间隔10秒
you are dog1