Question

I want to make a program that reads a file line by line and then writes those lines to another file. I want to solve this problem using two separate Threads. The first Thread reads a line and then passes it to the other Thread, which is responsible for writing that line to another file, via message. This process should be repeated until end of file is reached.

How can I do this?

Answer 1

What you want is a producer-consumer model. That’s not very hard to implement using two Thread objects and an ArrayBlockingQueue. Here’s some start-up code:

// we'll store lines of text here, a maximum of 100 at a time
ArrayBlockingQueue<String> queue = new ArrayBlockingQueue<String>(100);

// code of thread 1 (producer)
public void run() {
   while(/* lines still exist in input file */) {
       String line = // read a line of text
       queue.put(line); // will block if 100 lines are already inserted
   }
   // insert a termination token in the queue
}

// code of thread 2 (consumer)
public void run() {
   while(true) {
       String line = queue.take(); // waits if there are no items in the queue
       if(/* line is termination token */) break;
       // write line to file
   }   
}

Hope this helps. I cannot give the full code, it’s better if you try to fill the gaps yourself.