Java多线程的几种常见写法

多线程的几种写法

1）继承Thread

class MyThread extends Thread{@Overridepublic void run(){while(true){System.out.println("hello Thread");try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}}}}
public class Demo1 {public static void main(String[] args) {Thread t = new MyThread();t.start();while (true) {System.out.println("main");try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}}}
}

2）通过实现Runnable接口来实现

package Thread;
class MyRunnable implements Runnable{@Overridepublic void run() {while (true) {System.out.println("hello Thread");try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}}}}
public class Demo2 {public static void main(String[] args) {Thread t=new Thread(new MyRunnable());t.start();while(true){System.out.println("main");try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}}}
}

3）匿名内部类

package Thread;public class Demo3 {public static void main(String[] args) {Thread t=new Thread(){@Overridepublic void run(){while(true){System.out.println("hello thread");try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}}}};t.start();while(true){System.out.println("main");try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}}}
}

4）匿名内部类，针对Runnable

package Thread;public class Demo4 {public static void main(String[] args) {Thread t=new Thread(new MyRunnable(){@Overridepublic void run(){while(true){System.out.println("Thread");}}});t.start();while(true){System.out.println("main");}}
}

5）使用lambda表达式，lambda本质上就是针对匿名内部类的平替

package Thread;import org.w3c.dom.ls.LSOutput;public class Demo5 {public static void main(String[] args) throws InterruptedException {Thread t = new Thread(() -> {try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}});t.start();Thread.sleep(500);System.out.println(t.isAlive());}
}

上述的5种写法，本质上都是

1）要把线程执行的任务内容表示出来

2）通过Thread的start来创建/启动系统中的线程（Thread对象和操作系统中的线程是一一对象的关系）

catch语句中的代码

这个throw是继续再抛出新的异常

 try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}

这个是打印异常调用栈

try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}

2）再main方法中处理sleep有两种选择

1，throws

2，try catch

在线程的run中就只有一个选择了只能try catch，因为重写的时候，就要求方法的签名得是一样的

是否后台线程isDaemon()

关于线程各种属性的设置，都要放到start之前，一旦线程已经启动，开弓没有回头箭，再设置就来不及了

package Thread;import org.w3c.dom.ls.LSOutput;public class Demo5 {public static void main(String[] args) throws InterruptedException {Thread t = new Thread(() -> {try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}});
t.isDaemon();t.start();Thread.sleep(500);}
}

是否存活isAlive()

package Thread;import org.w3c.dom.ls.LSOutput;public class Demo5 {public static void main(String[] args) throws InterruptedException {Thread t = new Thread(() -> {try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}});t.start();Thread.sleep(4000);System.out.println(t.isAlive());}
}

是否中断isInterrupted()

1）第一种纯自己实现

需要让需要终止的线程的入口方法尽快执行结束（跳出循环，还是尽快return 都无所谓）

package Thread;public class Demo6 {private static Boolean isRunning =true;public static void main(String[] args) throws InterruptedException {Thread t=new Thread(() ->{while(isRunning){System.out.println("Thread");try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}}System.out.println("线程结束了");});t.start();System.out.println("main");Thread.sleep(5000);isRunning=false;System.out.println("变量结束");}
}

2）第二种

使用Thread提供的interrupt方法和isInterruptted方法来实现上述的效果，实际上Thread里面内置了一个，使用内置的标志位，功能要更强大

package Thread;public class Demo7 {public static void main(String[] args) throws InterruptedException {Thread t=new Thread(() ->{while(!Thread.currentThread().isInterrupted()){System.out.println("Thread");try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}}});t.start();t.interrupt();Thread.sleep(5000);System.out.println("结束进程");}
}

 当使用了Interrupt方法之后，此时，要不要结束，都是t线程自己决定的！！！

如果代码没有sleep，确实是直接修改了标志位就完了，有sleep，并且是触发Interrupt的时候，线程正在sleep，sleep被唤醒的同时，就会清楚刚才的标志位（又改回false）