Understanding Threads in java

Question

I'm quite new to the concepts of threads in JAVA and though I tried a couple of codes and they are working I really don't exactly understand whats happening in the background. For example I wrote this piece of code:

public class myThreadTest implements Runnable {
  private static void ping(String text, int count) 
                      throws InterruptedException {
    for (int i = 0; i<count; i++) {
      System.out.println("ping "+text+i+"...");
      Thread.sleep(1000);
    }
  }
  public void run() {
    try {
      ping("run ",10);
    } catch (InterruptedException e) {
    }
  }  
  public static void main(String[] args) {
    (new Thread(new myThreadTest())).start();
    try {
      ping("main ", 5);
    } catch (InterruptedException e) {
    }
 }
}

are there 2 threads being executed here one running from main and the other from the method run? Bcoz the output I get is main,run,main,run,run,main... something like that.

Sumit Singh · Accepted Answer · 2013-04-06 11:05:59Z

3

Yes ,the both executing concurrently.

A thread is a thread of execution in a program. The Java Virtual Machine allows an application to have multiple threads of execution running concurrently.

I am highly recommending this docs before starts coding .good luck

edited Apr 6, 2013 at 11:05

Sumit Singh

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answered Apr 6, 2013 at 11:02

Suresh Atta

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Comments

JohnnyQ · Accepted Answer · 2013-04-06 11:25:28Z

2

Threads in java have mainly to do with concurrency, which is s the notion of multiple things happening at the same time.A thread is an independent path of execution within a program.

From your program I can see your code is starting two threads at start up running the first command the for loop sleeping for 1 second then and then running run method and back and forth until the for loop is exhausted so the run continues to 9

answered Apr 6, 2013 at 11:25

JohnnyQ

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Comments

Brian Agnew · Accepted Answer · 2013-04-06 15:25:46Z

2

That's correct. Try printing the thread id in your ping() method to see that different threads are running (you can also name your threads and I follow that as a practise so I can understand which thread is doing what)

edited Apr 6, 2013 at 15:25

answered Apr 6, 2013 at 11:00

Brian Agnew

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Comments

xagyg · Accepted Answer · 2013-05-15 13:46:48Z

0

There are two threads. One of the threads is created and starts executing its run method asynchronously due to the start call in the main block. The other thread is executing the main method itself.

answered May 15, 2013 at 13:46

xagyg

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