How to iterate through ArrayBlockingQueue without memory allocation (GC delays)

I'm developing an Android Java game and trying to minimize memory allocation in the game loop. Every game objects on every frame draw its items, which stored in ArrayBlockingQueue. Every ForEach cycle allocates little portion memory for iterator and on large scales (60 times per second, thousands of objects and items), it causes 0.1-0.2 sec GC delays that affect FPS:

 ArrayBlockingQueue<Item> outputQueue = conveyor.getOutputQueue();

    for (Item item:outputQueue) {
        progress = 1.0f - (finishedCounter * stridePerItem);
        drawItem (camera, x, y, width, height, item, progress);
        finishedCounter++;
    }

All I need is to access all entries in ArrayBlockingQueue without changing it. Using ArrayBlockQueue.toArray() method makes copy of queue and allocates additional memory.

How to iterate through ArrayBlockingQueue without memory allocation (GC delays)?

p.s. The game simulates factory supply chains - queues. All of them accessed from two threads (OpenGL thread, GameLoop thread) and I need thread-safe Queues. Should I use any other type of Queue or special collections that can be accessed from different threads concurrently?

If you use Java 8 or later, you can use ArrayBlockingQueue#forEach in order to iterate.

If you look at the sources, you can easily see that forEach does not allocate an Iterator for this.

ArrayBlockingQueue<Item> outputQueue = conveyor.getOutputQueue();

    outputQueue.forEach(item-> {
        //your code
    });

Queue or ArrayBlockingQueue do not provide a way to iterate without using an Iterator or converting it to an array/other collection. This seems to be the only way to iterate over an ArrayBlockingQueue without allocating an extra object.

The disadvantage of this method is that you cannot access local variables that are not final or effectively final. You need to either create an object storing your variables or use a copy if you want to read local variables changed elsewhere.

You can also wrap variables if you need to change them in the iterator.

public class IntWrapper{//outside of the method
    private int value;
    //getter/setter/constructor
}

ArrayBlockingQueue<Item> outputQueue = conveyor.getOutputQueue();
final IntWrapper finishedCounterWrapper=new IntWrapper(finishedCounter);

outputQueue.forEach(item-> {
    progress = 1.0f - (finishedCounter * stridePerItem);
    drawItem (camera, x, y, width, height, item, progress);
    finishedCounterWrapper.setValue(finishedCounterWrapper.getValue());
});
finishedCounter=finishedCounterWrapper.getValue();

However, this allocates heap space for the IntWrapper, even if you can reuse the wrapper.