Java : multi threading not working

Question

I am trying this program in java but I am not getting any output when I put everything in the run() method

Main.java:

public class Main {

    static int line;
    static boolean ret = true;
    static BufferedReader br;

    /**
     * @param args
     * @throws IOException 
     */
    public static void main(String[] args) throws IOException {

            File f = new File("tere.dat");
            // boolean ret = f.createNewFile() ;
            br = new BufferedReader(new FileReader(f));

            new Test(br.readLine());
            new Test(br.readLine());
    }

}

Test.java:

public class Test extends Thread {

    private String input;
    static int thread_count = 0;

    public Test(String l)
    {
         input = l;
    }

    public void run()
    {
        System.out.println("Checking from other class  : This was printed from file :>>");
        System.out.println(input);
        String upper = input.toUpperCase();
        System.out.println("");
        System.out.println("The String in all UpperCase :" + upper);
    }
}

What I want to do is that I want to read lines from a file using two threads and then display whatever I get . I am new to Java

EDIT :

I was not using the start() method. Though even after using start() It reads only 2 lines from the file and stops. What could be the problem ?

jtahlborn · Accepted Answer · 2013-02-04 12:48:22Z

4

You have to start() your Threads.

Also, i would suggest reading a good tutorial on Threads and concurrency in Java before proceeding, as it's a complex subject.

answered Feb 4, 2013 at 12:48

jtahlborn

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Comments

Peter Lawrey · Accepted Answer · 2013-02-04 12:49:08Z

1

You need to start your thread with start() I suggest you not extend Thread but instead implement Runnable.

BTW: Unless you type impossibly fast, you won't see the difference in using threads. It will take about 0.1 milli-seconds to start the thread and finish it so unless you type much faster than that, it will make no difference.

answered Feb 4, 2013 at 12:49

Peter Lawrey

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2 Comments

Deepankar Bajpeyi Over a year ago

I know that. But I was just trying to understand the Thread Model :) thanks for the reply :)

Peter Lawrey Over a year ago

@DeepankarBajpeyi I suggest you input the two lines before start the threads, or just use hard coded Strings like "Hello" and "World".

partlov · Accepted Answer · 2013-02-04 12:49:20Z

1

You need to start threads:

(new Test(br.readLine())).start();

And also, you have to add some join to wait threads to finish because your main thread will finish execution before created threads.

answered Feb 4, 2013 at 12:49

partlov

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2 Comments

G. Bach Over a year ago

Is join really necessary? main thread is done after the two threads are created, so it doesnt need to wait for them to do whatever they do.

Deepankar Bajpeyi Over a year ago

It might finish before the threads, that is what I think partlov is trying to suggest

OschtärEi · Accepted Answer · 2013-02-04 12:49:30Z

1

You have to start them:

        (new Test(br.readLine())).start();
        (new Test(br.readLine())).start();

answered Feb 4, 2013 at 12:49

OschtärEi

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