如何使用三个不同的线程调用同一方法

Question

Suppose I have a method called Magic() I want to execute this method with three different thread. I know how to execute Magic() method with a single thread, but I am confuse, How do I do with three different threads?

Answer 1

Suppose I have a method called Magic() I want to execute this method with three different thread

Create a MagicTask class that represents the task that each Thread will execute and call the magic() method inside run() :

class MagicTask implements Runnable {
    public void run() {
        magic();
    }

    public void magic() { //do magic }

}

Then create three threads and pass it the task :

Thread t1 = new Thread(new MagicTask());
Thread t2 = new Thread(new MagicTask());
Thread t3 = new Thread(new MagicTask());

Then start the threads :

t1.start();
t2.start();
t3.start();

Note You can pass the same MagicTask instance to all three Thread instances as well. Remember that if MagicTask has state that can get inconsistent when accessed by different threads, you also need to make your class thread-safe by using intrinsic locking using synchronized or other such constructs which are out of the scope for this answer.

Answer 2

 class Multi3 implements Runnable{  
       public void run(){  
           System.out.println("thread is running...");  

            call();

       }  

       void call(){
            System.out.println("method call by"+Thread.currentThread().getName());
      }

    public static void main(String args[]){  
            Multi3 m1=new Multi3();  
            Thread t1 =new Thread(m1);  
            Thread t2 =new Thread(m1);  
            Thread t3 =new Thread(m1);  
            t1.start();  
            t2.start();
            t3.start();
    }  
}  

Here Thread t1,t2,t3 are calling the same method call().

Answer 3

If you are using Java 8, function references are straightforward:

public class Main {
    public static void magic() {
        System.out.println("this is magic");
    }

    public static void main(final String args[]) {
        new Thread(Main::magic).start();
        new Thread(Main::magic).start();
        new Thread(Main::magic).start();
    }
}

And if magic isn't a static method use:

public class Main {
    public void magic() {
        System.out.println("this is magic");
    }

    public static void main(final String args[]) {
        Main m = new Main();

        new Thread(m::magic).start();
        new Thread(m::magic).start();
        new Thread(m::magic).start();
    }
}

Answer 4

You can try Like.

I am dividing the task to different thread Try your own logic it just a simple even count,

public class CountNumber implements Runnable {

    int stop;
    int start;
    int totalEvenNo;

    public CountNumber(int start, int stop)
    {
        this.start=start;
        this.stop=stop;
    }

    public void run()
    {
    int total=  countEven(start, stop);
    System.out.println("Total Even numbers are :"+total);
    }
    public int countEven(int str,int stp)
    {
        for(int i=str;i<=stp;i++)
        {
            if(i%2==0)
            {
                totalEvenNo +=1;
                System.out.println(totalEvenNo);
            }
        }
        return totalEvenNo;
    }
   }

public class MainClassNumber {

    public static void main(String[] args) {
        System.out.println("Spawaning Thread.........");

            Thread t1 = new Thread(new CountNumber(0, 500000));
            Thread t2 = new Thread(new CountNumber(500001, 2000000));
            Thread t3 = new Thread(new CountNumber(2000001, 5000000));
            Thread t4 = new Thread(new CountNumber(5000001, 10000000));
            Thread t5 = new Thread(new CountNumber(10000001, 20000000));
            t1.start();
            t2.start();
            t3.start();
            t4.start();
            t5.start();

    }

}

Answer 5

Call it directly like magic(); And for better result synchronize that method like below

public synchronized void magic(){ 
              //your code 
}

Answer 6

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
class WorkerThread implements Runnable {

     public void run() {

        Magic();
    }
    private void Magic() {
// consider synchronizing this method, but if you do method will be accessable by one thread at a time.
     }

}

public class TestThreadPool {
     public static void main(String[] args) {
        ExecutorService executor = Executors.newFixedThreadPool(3)
        for (int i = 0; i < 3; i++) {
            Runnable worker = new WorkerThread();
            executor.execute(worker);
          }
        executor.shutdown();
       while (!executor.isTerminated()) {}

            }
}
}