线程实现的几种方式

1、继承Thread类

import java.util.*;public class Test {/*** 打字员线程,每秒打出多少字*/class Typist extends Thread {@Overridepublic void run() {int wordNum = new Random().nextInt(5);for(int i=1;i<=5;i++) {try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(this.getName() + "在第" + i + "秒打了" + wordNum + "个字");}}}public void printStart() {Thread typist1 = new Typist();typist1.setName("打字员A");Thread typist2 = new Typist();typist2.setName("打字员B");Thread typist3 = new Typist();typist3.setName("打字员C");typist1.start();typist2.start();typist3.start();}public static void main(String[] args) {/*** 主线程结束* 打字员A在第1秒打了4个字* 打字员B在第1秒打了2个字* 打字员C在第1秒打了4个字* 打字员C在第2秒打了4个字* 打字员B在第2秒打了2个字* 打字员A在第2秒打了4个字* 打字员A在第3秒打了4个字* 打字员C在第3秒打了4个字* 打字员B在第3秒打了2个字* 打字员A在第4秒打了4个字* 打字员B在第4秒打了2个字* 打字员C在第4秒打了4个字* 打字员B在第5秒打了2个字* 打字员C在第5秒打了4个字* 打字员A在第5秒打了4个字*/new Test().printStart();System.out.println("主线程结束");}
}

2、实现Runnable接口（推荐方式）

import java.util.*;public class Test {/*** 打字员线程,每秒打出多少字*/class Typist implements Runnable {@Overridepublic void run() {int wordNum = new Random().nextInt(5);for(int i=1;i<=5;i++) {try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName() + "在第" + i + "秒打了" + wordNum + "个字");}}}public void printStart() {Typist typist1 = new Typist();Thread t1 = new Thread(typist1);Typist typist2 = new Typist();Thread t2 = new Thread(typist2);Typist typist3 = new Typist();Thread t3 = new Thread(typist3);t1.setName("打字员A");t2.setName("打字员B");t3.setName("打字员C");t1.start();t2.start();t3.start();}public static void main(String[] args) {new Test().printStart();System.out.println("主线程结束");}
}

3、实现Callable接口，可以从线程中获取返回值

import lombok.Data;import java.util.*;
import java.util.concurrent.*;public class Test {/*** 打字员线程,每秒打出多少字*/@Dataclass Typist implements Callable<Integer> {private String name;@Overridepublic Integer call() throws Exception {int wordCount = 0;int wordNum = new Random().nextInt(5);for(int i=1;i<=5;i++) {try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}wordCount += wordNum;System.out.println(this.getName() + "在第" + i + "秒打了" + wordNum + "个字");}return wordCount;}}public void printStart() throws ExecutionException, InterruptedException {Typist t1 = new Typist();t1.setName("打字员A");FutureTask<Integer> futureTask1 = new FutureTask<>(t1);Thread thread1 = new Thread(futureTask1);thread1.start();Typist t2= new Typist();t2.setName("打字员B");FutureTask<Integer> futureTask2 = new FutureTask<>(t2);Thread thread2 = new Thread(futureTask2);thread2.start();System.out.println(t1.getName() + "一共打了" + futureTask1.get() + "个字");//get()方法阻塞System.out.println(t2.getName() + "一共打了" + futureTask2.get() + "个字");}public static void main(String[] args) throws ExecutionException, InterruptedException {new Test().printStart();System.out.println("主线程任务结束");}
}

FutureTask.get()方法阻塞，程序的运行后，最后打印【主线程任务结束】

4、Callable接口+线程池（推荐方式，可以从线程中获取返回值）

import lombok.Data;import java.util.*;
import java.util.concurrent.*;public class Test {/*** 打字员线程,每秒打出多少字*/@Dataclass Typist implements Callable<Integer> {private String name;@Overridepublic Integer call() throws Exception {int wordCount = 0;int wordNum = new Random().nextInt(5);for(int i=1;i<=5;i++) {try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}wordCount += wordNum;System.out.println(this.getName() + "在第" + i + "秒打了" + wordNum + "个字");}return wordCount;}}public void printStart() throws ExecutionException, InterruptedException {//固定大小线程池ExecutorService executorService = Executors.newFixedThreadPool(3);Typist t1 = new Typist();t1.setName("打字员A");Typist t2 = new Typist();t2.setName("打字员B");Typist t3 = new Typist();t3.setName("打字员C");Future<Integer> f1 = executorService.submit(t1);//非阻塞Future<Integer> f2 = executorService.submit(t2);Future<Integer> f3 = executorService.submit(t3);executorService.shutdown();System.out.println(t1.getName() + "一共打了" + f1.get() + "个字") ;//阻塞System.out.println(t2.getName() + "一共打了" + f2.get() + "个字") ;System.out.println(t3.getName() + "一共打了" + f3.get() + "个字") ;}public static void main(String[] args) throws ExecutionException, InterruptedException {new Test().printStart();System.out.println("主线程任务结束");}
}

Future.get()方法阻塞等待t1线程结束，获取线程执行完成后的返回值

应用场景：这种方式适合大数据量计算时，开启多个线程分别执行部分数据，最后通过get()方法的返回值再合并各个线程计算结果，经典的map-reduce