queue with time stamped elements within a time period

user_759326 0
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I want to store in a queue, datastructure does not matter, only the elements that I have inserted within say last 5 minutes from current time. Anything older should get removed - so that any time I get the size of the queue it will give count of the objects inserted in last 5 minutes.

Basically all I have to know is how many times my app has made a http call to a sever in last 5 minutes before making the next call.

If anyone knows of some existing library that may have this implementation please share.

data-structures queue java
3 Answers

I have implement a FadingLinkedList like

public class FadingLinkedList<E> {

private transient Entry<E> header = new Entry<E>(null, null);

/**
 * ms
 */
private long livingTime;

/**
 * Constructs FadingLinkedList with elements of living time livingTime in
 * milliseconds
 */
public FadingLinkedList(long livingTime) {
    this.livingTime = livingTime;
}

/**
 * remove all faded elements,
 *
 * @return the count of not faded
 */
public synchronized int removeFaded() {
    long now = System.nanoTime();
    int count = 0;
    Entry<E> prev = header;// the last living Entry in the loop
    for (Entry<E> e = header.next; e != null; e = e.next) {
        if (TimeUnit.NANOSECONDS.toMillis(now - e.birthTime) >= livingTime) {
            // cut off this list here.
            prev.next = null;
            break;
        }
        count++;
        prev = e;
    }
    return count;
}

/**
 * Returns the number of elements that not faded.
 */
public int size() {
    return removeFaded();
}

public synchronized void push(E e) {
    Entry<E> newEntry = new Entry<E>(e, header.next);
    header.next = newEntry;
}

private static class Entry<E> {
    E element;
    Entry<E> next;
    long birthTime;

    Entry(E element, Entry<E> next) {
        this.element = element;
        this.next = next;
        this.birthTime = System.nanoTime();
    }
}

public synchronized void clear() {
    header.next = null;
}

public synchronized int getAndClear() {
    int size = size();
    clear();
    return size;
}

}

user_17707160
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