三种创建线程的方式:
- Thread类:继承Thread类(重点)
- Runnable接口:实现Runnable接口(重点)
- Callable接口:实现Callable接口
1.Thread类
创建线程方式一:继承Thread类;重新run方法;创建对象,调用start方法
注意:线程开启不一定立即执行,由CPU调度执行
//创建线程方式一:继承Thread类;重新run方法;创建对象,调用start方法
//注意:线程开启不一定立即执行,由CPU调度执行
public class testTread01 extends Thread {
//线程入口点
@Override
public void run() {
//线程体
for(int i = 0; i < 10; i ++){
System.out.println("我在学习代码" + i);
}
}
}
public class Demo01 {
//main线程,主线程
public static void main(String[] args) {
//创建一个线程对象
testTread01 tt = new testTread01();
//调用start方法开启线程
tt.start();
for(int i = 0; i < 100; i ++){
System.out.println("我在看代码" + i);
}
}
}
例子:下载图片
import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
//练习thread,实现多线程同步下载图片
public class testThread02 extends Thread{
private String url;/网络图片地址
private String name;//保存的文件名
public testThread02(String url, String name) {
this.url = url;
this.name = name;
}
@Override
public void run() {
webDownLoder wb = new webDownLoder();
wb.downLoder(url,name);
System.out.println("上传图片" + name);
}
public static void main(String[] args) {
testThread02 tt = new testThread02("https://ss.html.cn/newimg88/2016/06/beian-gov-cn.png","1.png");
tt.start();
}
}
//下载器
class webDownLoder{
//下载方法
public void downLoder(String url,String name){
try {
//导入commons.io.jar包,使用其中FileUtils类中的copyURLToFile方法
FileUtils.copyURLToFile(new URL(url),new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("IO异常,downLoder出现问题");
}
}
}
导入jar包的方法:创建lib包,复制jar包到lib目录下,右键lib选择Add as library…
2.实现Runnable接口
步骤:
定义testThread03实现类实现Runnable接口
实现run()方法,编写线程执行体
创建实现类对象,创建线程对象线程,调用start()方法启动线程
//创建线程的方式2: 实现Runnable接口;实现run()方法;创建线程对象,调用start()方法启动线程
public class testThread03 implements Runnable{
@Override
public void run() {
for(int i = 0;i <10; i ++){
System.out.println("我是线程体" + i);
}
}
public static void main(String[] args) {
//创建Runnable接口的实现类对象
testThread03 tt = new testThread03();
//创建线程对象,通过线程对象来开启线程-----代理
// Thread th = new Thread(tt);
// th.start();
new Thread(tt).start();
for(int i = 0;i <50; i ++){
System.out.println("我是主线程体" + i);
}
}
}
利用Runnable接口,下载图片:
import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
//练习thread,实现多线程同步下载图片
public class testThread04 implements Runnable{
private String url;
private String name;
public testThread04(String url, String name) {
this.url = url;
this.name = name;
}
@Override
public void run() {
webDownLoder02 wb = new webDownLoder02();
wb.downLoder(url,name);
System.out.println("上传图片" + name);
}
public static void main(String[] args) {
testThread04 t = new testThread04("https://ss.html.cn/upload/article/000/000/016/603279dddcd25168.jpg-600","1.png");
new Thread(t).start();
}
}
//下载器
class webDownLoder02{
//下载方法
public void downLoder(String url,String name){
try {
FileUtils.copyURLToFile(new URL(url),new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("IO异常,downLoder出现问题");
}
}
}
Thread和Runnable对比:
-
继承Thread类:启动线程:子类对象.start();
不建议使用,避免OOP编程单继承的局限性 -
实现Runnbable接口:启动线程:传入目标对象.Thread对象.start()
推荐使用Runnable,避免单进程局限性,方便同一个对象被多个线程使用。
模拟抢火车票
//问题:多个线程操作同一个资源,进程不安全,数据紊乱
public class testThread05 implements Runnable{
private int ticketNums = 10;
@Override
public void run() {
while(true){
if(ticketNums <= 0){
break;
}
//模拟时延
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
//获得当前执行线程的名字
System.out.println(Thread.currentThread().getName() + "拿到了第" + ticketNums-- + "票");
}
}
public static void main(String[] args) {
testThread05 t = new testThread05();
new Thread(t,"凸凸").start();
new Thread(t,"凹凹").start();
new Thread(t,"黄牛").start();
}
}
模拟龟兔赛跑
//模拟龟兔赛跑
public class Race implements Runnable {
private static String winner;
@Override
public void run() {
for(int i = 0; i <= 100; i ++){
//模拟兔子睡觉
if(Thread.currentThread().getName().equals("兔子")&& (i %10 == 0)){
try {
Thread.sleep(5);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//判断比赛是否结束
boolean flag = gameOver(i);
if(flag == true){
break;
}
System.out.println(Thread.currentThread().getName() + "跑了" + i + "步");
}
}
//判断比赛是否结束
private boolean gameOver(int step){
if(winner != null){
return true;
}else if(step >= 100){
winner = Thread.currentThread().getName();
System.out.println("winner is" + winner);
return true;
}else {
return false;
}
}
public static void main(String[] args) {
Race race = new Race();
new Thread(race,"兔子").start();
new Thread(race,"乌龟").start();
}
}
3.callable接口(了解)
实现Callable接口,需要返回值类型
重写call方法,需要抛出方法
创建目标对象
创建执行服务:ExecutorService ser=Executors.newFixedThreadPool(1);
提交执行:Future result1=ser.submit(t1);
获取结果:boolean r1=result1.get();
关闭服务:ser.shutdownNow();
import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.*;
public class testCallable implements Callable<Boolean> {
private String url;
private String name;
public testCallable(String url, String name) {
this.url = url;
this.name = name;
}
@Override
public Boolean call() {
webDownLoder03 wb = new webDownLoder03();
wb.downLoder(url,name);
System.out.println("上传图片" + name);
return true;
}
public static void main(String[] args) throws ExecutionException, InterruptedException {
testCallable t1 = new testCallable("https://ss.html.cn/upload/article/000/000/016/603279dddcd25168.jpg-600","1.png");
//创建执行服务
ExecutorService ser= Executors.newFixedThreadPool(1);
//提交执行
Future<Boolean> r1 = ser.submit(t1);
//获取结果
boolean rs1 = r1.get();
//关闭服务
ser.shutdownNow();
}
}
class webDownLoder03{
//下载方法
public void downLoder(String url,String name){
try {
FileUtils.copyURLToFile(new URL(url),new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("IO异常,downLoder出现问题");
}
}
}
优点:
可以定义返回值
可以抛出异常