TopList

toplist.groovy

class TopList<E extends Comparable> {

    @Delegate
    private List items
    private int maxSize
    private Comparator<E> comparator = new ReverseComparator()

    TopList(int maxSize) {
        this.maxSize = maxSize
        this.items = new ArrayList(maxSize)
    }

    boolean add(E item) {

        insertInOrder(item)

        trimToSize()

        true
    }

    private def insertInOrder(E item) {

        int index = Collections.binarySearch(items, item, comparator)

        int insertionPoint = index < 0 ? Math.abs(index + 1) : index

        items.add(insertionPoint, item)
    }

    private void trimToSize() {
        while (items.size() > maxSize) {
            items.remove(items.size()-1)
        }
    }

    // Reverses the comparison to make the order descending
    class ReverseComparator implements Comparator<E> {
        int compare(E a, E b) {
            b.compareTo(a)
        }
    }

}