Java dynamic list in while(true) loop

You are describing the Producer / Consumer pattern. Java has thread safe ways to achieve this. The easiest would be to use java.util.concurrent.BlockingQueue<E>

The way to use it is to share the BlockingQueue between a Consumer (thread) and one or more Producer threads. The Consumer blocks with the method E Queue.take(). The clients add to the Queue with method Queue.offer(E).

First create the BlockingQueue:

BlockingQueue<MyObject> myQueue = new LinkedBlockingQueue<MyObject>(int capacity);

The server thread will look something like this:

    BlockingQueue<MyObject> myQueue;
    // A constructor which receives the BlockingQueue object

    // Main Loop
    boolean isInterrupted = false;

    while(!isInterrupted) {
        try {
            MyObject object = myQueue.take();   // Will block
            // Process object
        } catch (InterruptedException e) {
            isInterrupted = true;
        }
    }

And for each producer thread, pass the BlockingQueue object to each, and use:

BlockingQueue<MyObject> myQueue;
// A constructor which receives the BlockingQueue object

// Create MyObjects
myQueue.offer(myObject);   // Will add to the queue

There is the concept of a queue capacity. If the producers add too quickly queue may reach capacity. An offer can fail in this case. See the javadoc LinkedBlockingQueue for full details