Package org.apache.lucene.util

Class CollectionUtil

  • public final class CollectionUtil
extends Object
    Methods for manipulating (sorting) collections. Sort methods work directly on the supplied lists and don't copy to/from arrays before/after. For medium size collections as used in the Lucene indexer that is much more efficient.
    NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

    • Method Detail

      • quickSort

        public static <T> void quickSort​(List<T> list,
                                 Comparator<? super T> comp)
        Sorts the given random access List using the Comparator. The list must implement RandomAccess. This method uses the quick sort algorithm, but falls back to insertion sort for small lists.
        Throws:
        IllegalArgumentException - if list is e.g. a linked list without random access.

      • quickSort

        public static <T extends Comparable<? super T>> void quickSort​(List<T> list)
        Sorts the given random access List in natural order. The list must implement RandomAccess. This method uses the quick sort algorithm, but falls back to insertion sort for small lists.
        Throws:
        IllegalArgumentException - if list is e.g. a linked list without random access.

      • mergeSort

        public static <T> void mergeSort​(List<T> list,
                                 Comparator<? super T> comp)
        Sorts the given random access List using the Comparator. The list must implement RandomAccess. This method uses the merge sort algorithm, but falls back to insertion sort for small lists.
        Throws:
        IllegalArgumentException - if list is e.g. a linked list without random access.

      • mergeSort

        public static <T extends Comparable<? super T>> void mergeSort​(List<T> list)
        Sorts the given random access List in natural order. The list must implement RandomAccess. This method uses the merge sort algorithm, but falls back to insertion sort for small lists.
        Throws:
        IllegalArgumentException - if list is e.g. a linked list without random access.

      • insertionSort

        public static <T> void insertionSort​(List<T> list,
                                     Comparator<? super T> comp)
        Sorts the given random access List using the Comparator. The list must implement RandomAccess. This method uses the insertion sort algorithm. It is only recommended to use this algorithm for partially sorted small lists!
        Throws:
        IllegalArgumentException - if list is e.g. a linked list without random access.

      • insertionSort

        public static <T extends Comparable<? super T>> void insertionSort​(List<T> list)
        Sorts the given random access List in natural order. The list must implement RandomAccess. This method uses the insertion sort algorithm. It is only recommended to use this algorithm for partially sorted small lists!
        Throws:
        IllegalArgumentException - if list is e.g. a linked list without random access.