并发
1.初识并发问题
// 多个线程同时操作一个对象
// 买火车票
// 发现问题：多个线程操作同一个资源的情况下，线程不安全
public class TestThread4 implements Runnable{
// 票数
private int ticketNums = 10;
public void run(){
while (true){
if (this.ticketNums <= 1){
break;
}
// 模拟延时
try {
Thread.sleep( 200);
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+"---->拿到了第"+ticketNums+"————>票");
this.ticketNums--;
}
}
public static void main(String[] args) {
TestThread4 ticket = new TestThread4();
new Thread(ticket,"小明").start();
new Thread(ticket,"老师").start();
new Thread(ticket,"黄牛").start();
}
}
2.龟兔赛跑案例
// 模拟龟兔赛跑
public class Race implements Runnable{
// 定义胜利者
private static String winner;
@Override
public void run() {
for (int i = 0; i <= 100; i++) {
// 模拟兔子休息
if(Thread.currentThread().getName() == "兔子"){
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
// 判断比赛是否结束
boolean flag = this.gameOver(i);
//如果比赛结束
if(flag){
break;
}
System.out.println(Thread.currentThread().getName() + "---->跑了"+i+"步");
}
}
private boolean gameOver(int step){
// 判断是否有胜利者
if(winner !=null){
return true;
}else {
if(step >= 100){
winner = Thread.currentThread().getName();
System.out.println("winner is" +winner);
return true;
}
return false;
}
}
// 判断是否完成比赛
public static void main(String[] args) {
Race race = new Race();
new Thread(race,"兔子").start();
new Thread(race,"乌龟").start();
}
}
3.实现Callable接口
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实现Callable接口，需要返回值类型。
-
重写call方法，需要抛出异常。
-
创建目标对象。
-
创建执行服务:ExecutorService ser = Executors.newFixedThreadPool(1);
-
提交执行:Future<Boolean> result1 = ser.submit(t1);
-
获取结果: boolean r1 = result1.get()
-
关闭服务:ser.shutdownNow();
import org.apache.commons.io.FileUtils;标签：String,Thread,url,接口,Callable,并发,new,public,name From： https://www.cnblogs.com/yuan947022015/p/17654228.html
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.*;
// 线程实现方式三
public class TestCallable implements Callable<Boolean> {
private String url; //地址
private String name;//文件名
public TestCallable(String url, String name) {
this.url = url;
this.name = name;
}
// 下载图片线程执行体
@Override
public Boolean call() {
WebDownLoader webDownloader = new WebDownLoader();
webDownloader.downLoader(url, name);
System.out.println("下载了文件名为：" + name);
return true;
}
public static void main(String[] args) throws ExecutionException, InterruptedException {
TestCallable t1 = new TestCallable("https://img0.baidu.com/it/u=3021883569,1259262591&fm=253&app=120&size=w931&n=0&f=JPEG&fmt=auto?sec=1692982800&t=5858b3800995bb2c1af459caaab34932", "1.jpg");
TestCallable t2 = new TestCallable("https://img0.baidu.com/it/u=3021883569,1259262591&fm=253&app=120&size=w931&n=0&f=JPEG&fmt=auto?sec=1692982800&t=5858b3800995bb2c1af459caaab34932", "2.jpg");
TestCallable t3 = new TestCallable("https://img0.baidu.com/it/u=3021883569,1259262591&fm=253&app=120&size=w931&n=0&f=JPEG&fmt=auto?sec=1692982800&t=5858b3800995bb2c1af459caaab34932", "3.jpg");
// 创建执行服务
ExecutorService ser = Executors.newFixedThreadPool(3);
// 提交换行
Future<Boolean> r1 = ser.submit(t1);
Future<Boolean> r2 = ser.submit(t2);
Future<Boolean> r3 = ser.submit(t3);
// 获取结果
boolean rs1 = r1.get();
boolean rs2 = r2.get();
boolean rs3 = r3.get();
// 关闭服务
ser.shutdownNow();
}
public static void downLoader(String url, String name) {
try {
FileUtils.copyURLToFile(new URL(url), new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("Io异常，downloader出现问题");
}
}
}
// 下载器
class WebDownLoader {
// 下载方法
public void downLoader(String url, String name) {
try {
FileUtils.copyURLToFile(new URL(url), new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("Io异常，downloader出现问题");
}
}
}