JAVA多线程并发——创建线程

第一章：线程的创建与实现

文章目录

• JAVA多线程并发——创建线程
• 一、继承Thread类
• 二、实现runnable接口
• 三、简单匿名内部类写法
• 四、实现Callable接口
• 五、线程池

一、继承Thread类

代码示例：

public class ExtendThread {public static void main(String[] args) {Thread thread1 = new MyThread(1);Thread thread2 = new MyThread(2);thread1.start();thread2.start();}public static class MyThread extends Thread {int num;public MyThread(int num){this.num = num;}@Overridepublic void run() {System.out.println("我是线程"+ num);}}
}

运行结果：

二、实现runnable接口

代码示例：

/*** 通过实现Runnable接口创建线程* 线程无返回值*/
public class implementRunnable {public static void main(String[] args) throws InterruptedException {Runnable runnable1 = new MyRunnable(1);Runnable runnable2 = new MyRunnable(2);Thread thread1 = new Thread(runnable1);Thread thread2 = new Thread(runnable2);thread1.start();Thread.sleep(1000);thread2.start();}public static class MyRunnable implements Runnable {int num;public MyRunnable(int num) {this.num = num;}@Overridepublic void run() {System.out.println("我是线程" + num);}}
}

运行结果：

三、简单匿名内部类写法

代码示例：

public class innerRunnable {public static void main(String[] args) {System.out.println("我是原线程");Thread thread = new Thread(new Runnable() {@Overridepublic void run() {System.out.println("我是新线程");}});thread.start();}
}

运行结果：

四、实现Callable接口

该方式创建线程可以获取新线程的返回值，上面的方法均无返回值
示例代码：

/*** 通过实现Callable接口实现* 线程有返回值*/
public class implementCallable {public static void main(String[] args) throws ExecutionException, InterruptedException {MyCallable myCallable1 = new MyCallable(1);FutureTask futureTask1 = new FutureTask<>(myCallable1);Thread thread1 = new Thread(futureTask1);thread1.start();String str1 = futureTask1.get();System.out.println("线程返回值：" + str1);MyCallable myCallable2 = new MyCallable(2);FutureTask futureTask2 = new FutureTask<>(myCallable2);Thread thread2 = new Thread(futureTask2);thread2.start();String str2 = futureTask2.get();System.out.println("线程返回值: " + str2);}public static class MyCallable implements Callable{int num;public MyCallable(int num){this.num = num;}@Overridepublic String call() throws Exception {System.out.println("新线程" + num + "开始执行");return "创建了线程" + num;}}
}

运行结果：

五、线程池

推荐使用最后一种，new ThreadPoolExecutor(int corePoolSize,
int maximumPoolSize,
long keepAliveTime,
TimeUnit unit,
BlockingQueue workQueue,
RejectedExecutionHandler handler) ;

/*** 通过Executor的几个默认的线程池配置*/
public class ByExecutor {public static void main(String[] args) {//createCachedThreadPool();//createFixThreadPool();//createScheduledThreadPool();//createSingleThreadPool();createByThreadPoolExecutor();}/*** newCachedThreadPool* 核心线程数无限大* 会重复利用之前的线程* 没有旧线程会创建新线程*/private static void createCachedThreadPool() {ExecutorService threadPool = Executors.newCachedThreadPool();while (true) {threadPool.execute(new Runnable() {@Overridepublic void run() {System.out.println("我是线程" + Thread.currentThread().getName());}});try {Thread.sleep(3000);} catch (InterruptedException e) {e.printStackTrace();}}}/*** newFixedThreadPool* 固定线程数* 当前没有可用线程则会等待* 不会创建新线程*/private static void createFixThreadPool() {ExecutorService threadPool = Executors.newFixedThreadPool(3);while (true) {threadPool.execute(new Runnable() {@Overridepublic void run() {System.out.println("我是线程 " + Thread.currentThread());}});}}/*** newScheduledThreadPool* 支持延时执行* 固定线程数*/private static void createScheduledThreadPool() {ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(2);long delay = 5;System.out.println(new Date().getSeconds());while (true) {scheduledThreadPool.schedule(new Runnable() {@Overridepublic void run() {System.out.println("我是定时线程：" + Thread.currentThread() + new Date().getSeconds());}}, delay, TimeUnit.SECONDS);}}/*** newSingleThreadPool* 单线程*/private static void createSingleThreadPool() {ExecutorService threadPool = Executors.newSingleThreadExecutor();while (true) {threadPool.execute(new Runnable() {@Overridepublic void run() {System.out.println("我是single线程 " + Thread.currentThread());}});}}/*** 推荐的使用线程池的方式，通过构造方法创建*/private static void createByThreadPoolExecutor() {ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2,2,3,TimeUnit.SECONDS,new LinkedBlockingQueue<>(2),new ThreadPoolExecutor.CallerRunsPolicy());for (int i = 0; i < 10; i++) {//创建任务Runnable runnable = new Runnable() {@Overridepublic void run() {try {Thread.sleep(20);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName());}};// 将任务交给线程池管理threadPoolExecutor.execute(runnable);}}
}