如何使用多个线程调用方法

Question

I have a method sendMail(list) . This method will send the mails to the recipients which are there in the list.

public void sendMail(List<DTO> dto) {


        for(DTO individualObject: dto) {
            
            bulkMailSender.sendSimpleMessage(individualObject.getEmail(),masterDetails.getMailSubject() , content, masterDetails.getMailFrom(), individualObject); 
            try {
                TimeUnit.MINUTES.sleep(Long.parseLong(individualObject.getTimegap().trim()));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    }

}

I have this kind of method. I want to run this method Thread based, when one thread is executing the mails, I should allow the other thread to access sendMail and send simultaneously together. Each and every individualObject contains it's own sleep time.

How can I make it worked with the multiple threads.

Let's take an example

import java.util.concurrent.TimeUnit;

public class SleepClass {
    public static void main(String[] args) {
        SleepClass s= new SleepClass();
        s.m1(10000);
        s.m1(20000);
        
        
    }
    
    public void m1(int time) {
        
        for(int i = 0; i< 3; i++) {
            System.out.println(i);
            try {
                Thread.sleep(time);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        
    }

}

In the above example I have a regular method and it is executing one by one. How can make it simultaneous execution

Answer 1

You have to put your logic in a Runnable and launch it using new Thread(runnable).start() . To pass parameters to each runnable define them as class variables so you can pass them via the constructor and use them in the run method:

public class SleepClass {

    public static void main(String[] args) {
        SleepClass s= new SleepClass();
        s.m1(10000);
        s.m1(20000);
    }
    
    public void m1(int time) {
        for(int i = 0; i< 3; i++) {
            new Thread(new Launcher(i,time)).start();
        }
    }

    public class Launcher implements Runnable {
        int i;
        int time;
        public Launcher(int i, int time) {
            this.i=i;
            this.time=time;
        }
        @Override
        public void run() {
            System.out.println(i);
            try {
                Thread.sleep(time);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }                   
        }
        
    }
}

Answer 2

if you need simultaneous execution and each time new thread you can find the solution here

public class SleepClass {
    public static void main(String[] args) {
        SleepClass s= new SleepClass();
        s.m2(500);
        s.m2(1000);
    }
    
    public void m2(int time) {
        SleepClass s= new SleepClass();
        new Thread(() -> {
            s.m1(time);
        }).start();
    }
    
    public void m1(int time) {
        
        for(int i = 0; i<= 10; i++) {
            System.out.println(i);
            try {
                Thread.sleep(time);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        
    }

}