守护线程
package com.hanyxx.thread;
import lombok.SneakyThrows;
/**
* @author layman
* @date 2021/2/5
*/
public class ThreadDaemon04 {
public static void main(String[] args) throws InterruptedException {
demo04 demo04 = new demo04();
//当把demo04设置为守护线程时,主线程结束时,demo04就会结束。
demo04.setDaemon(true);
demo04.start();
Thread.sleep(2000);
System.out.println("main线程结束");
}
}
class demo04 extends Thread{
@SneakyThrows
@Override
public void run() {
while(true){
System.out.println("time= "+System.currentTimeMillis());
Thread.sleep(500);
}
}
}
线程安全
验证局部变量线程安全
package com.hanyxx.thread;
import lombok.SneakyThrows;
/**
* @author layman
* @date 2021/2/5
*/
public class Demo05 {
public static void main(String[] args) {
Demo05Service service = new Demo05Service();
Demo05ThreadA threadA = new Demo05ThreadA(service);
threadA.start();
Demo05ThreadB threadB = new Demo05ThreadB(service);
threadB.start();
}
}
class Demo05Service{
@SneakyThrows
public void changeNum(String username){
int number;
if("layman".equals(username)){
number = 100;
//线程睡眠,让后续线程可以修改number的值
Thread.sleep(2000);
}else{
number = 200;
}
System.out.println("username: ["+username+"] number: ["+number+"]");
}
}
class Demo05ThreadA extends Thread{
private Demo05Service service;
public Demo05ThreadA(Demo05Service service){
this.service = service;
}
@SneakyThrows
@Override
public void run() {
while (true) {
Thread.sleep(1000);
service.changeNum("layman");
}
}
}
class Demo05ThreadB extends Thread{
private Demo05Service service;
public Demo05ThreadB(Demo05Service service){
this.service = service;
}
@SneakyThrows
@Override
public void run() {
while (true) {
Thread.sleep(1000);
service.changeNum("菠菜饭团");
}
}
}
验证成员变量线程不安全
package com.hanyxx.thread;
import lombok.SneakyThrows;
/**
* @author layman
* @date 2021/2/5
*/
public class Demo05 {
public static void main(String[] args) {
Demo05Service service = new Demo05Service();
Demo05ThreadA threadA = new Demo05ThreadA(service);
threadA.start();
Demo05ThreadB threadB = new Demo05ThreadB(service);
threadB.start();
}
}
class Demo05Service{
int number;
@SneakyThrows
public void changeNum(String username){
if("layman".equals(username)){
number = 100;
//线程睡眠,让后续线程可以修改number的值
Thread.sleep(2000);
}else{
number = 200;
}
System.out.println("username: ["+username+"] number: ["+number+"]");
}
}
class Demo05ThreadA extends Thread{
private Demo05Service service;
public Demo05ThreadA(Demo05Service service){
this.service = service;
}
@SneakyThrows
@Override
public void run() {
while (true) {
Thread.sleep(1000);
service.changeNum("layman");
}
}
}
class Demo05ThreadB extends Thread{
private Demo05Service service;
public Demo05ThreadB(Demo05Service service){
this.service = service;
}
@SneakyThrows
@Override
public void run() {
while (true) {
Thread.sleep(1000);
service.changeNum("菠菜饭团");
}
}
}
结论:
- 局部变量在方法内部,是私有的。这意味着它永远是线程安全的。
- 成员变量为类所有,它不是线程安全的。