如何同时执行三个线程？

Question

This is my code which i tried but my main class is not there because i don't know how to use that one

//first thread

class firstthread extends Thread
{
   public void run(){
     for(int i=0;i<1000;i++)
     {
          System.out.println(i);
     }}
}

//second thread

class secondthread extends Thread
{
   public void run(){
     for(int i=0;i<1000;i++)
     {
          System.out.println(i);
     }}
}

Answer 1

Whatever you have written is incomplete code, to create a thread you need to extend Thread class or implement Runnable interface and then override its public void run() method.

To create a thread you need to override the method public void run

Then to start the threads you need to call its start() method.

A simple complete example

class MyThread extends Thread {
   String name;
   public void run(){
      for(int i=0;i<1000;i++) {
         System.out.println("Thread name :: "+name+" : "i);
     }
   }
}
class Main{
    public static void main(String args[]){
        MyThread t1 = new MyThread();
        t1.name = "Thread ONE";
        MyThread t2 = new MyThread();
        t2.name = "Thread TWO";
        MyThread t3 = new MyThread();
        t3.name = "Thread THREE";
        t1.start();
        t2.start();
        t3.start();
    }
}

Answer 2

首先覆盖run方法，然后在main（）中创建线程类的对象，然后调用start方法。

Answer 3

public static void main(String[] args) {
    for (int i = 0; i < 3; i++) {
        new Thread() {
            public void run() {
                for(int y=0;y<1000;y++)
                 {
                      System.out.println(y);
                 }
            };
        }.start();
    }
}

Answer 4

You can't just put some code in your class body.

You need a method to have the code in, the method being run() in case of thread.

Instead of copy-pasting the code, I'll point you to the official documentation where you can find some examples.

Answer 5

Sample program given below. Since there is no synchronization code, there output is mixed from the three threads

public class ThreadTest implements Runnable{

@Override
public void run() {
    System.out.print(Thread.currentThread().getId() + ": ");
    for(int i=0;i<100;i++)
        System.out.print(i + ", ");
    System.out.println();

}
public static void main(String[] args) {
    for(int i=0;i<3;i++){
        new Thread(new ThreadTest()).start();
    }
}
}