2013/3/2 <[email protected]>
> Author: tn
> Date: Sat Mar 2 18:12:46 2013
> New Revision: 1451914
>
> URL: http://svn.apache.org/r1451914
> Log:
> [COLLECTIONS-366] Added ListUtils.range methods.
>
> Modified:
>
> commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java
>
> Modified:
> commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java
> URL:
> http://svn.apache.org/viewvc/commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java?rev=1451914&r1=1451913&r2=1451914&view=diff
>
> ==============================================================================
> ---
> commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java
> (original)
> +++
> commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java
> Sat Mar 2 18:12:46 2013
> @@ -507,6 +507,9 @@ public class ListUtils {
> return -1;
> }
>
> + // partition
> +
> //-------------------------------------------------------------------------
> +
> /**
> * Returns consecutive {@link List#subList(int, int) sublists} of a
> * list, each of the same size (the final list may be smaller). For
> example,
> @@ -579,4 +582,99 @@ public class ListUtils {
> return list.isEmpty();
> }
> }
> +
> + // range
> +
> //-------------------------------------------------------------------------
> +
> + /**
> + * Returns an unmodifiable List of integers in the range [0, size -
> 1].
> + * <p>
> + * The returned list does not store the actual numbers, but checks
> + * if a given number would be contained in the defined range. A call
> + * to {@link #contains(Object)} is very fast - O(1).
> + *
> + * @see #range(int,int)
> + *
> + * @param size the size of the returned list
> + * @return an unmodifiable list of integers in the range [0, size - 1]
> + * @throws IllegalArgumentException if from > to
> + * @since 4.0
> + */
> + public static List<Integer> range(final int size) {
> + return range(0, size - 1);
> + }
> +
> + /**
> + * Returns an unmodifiable List of integers in the range [from, to].
> + * <p>
> + * The returned list does not store the actual numbers, but checks
> + * if a given number would be contained in the defined range. A call
> + * to {@link #contains(Object)} is very fast - O(1).
> + * <p>
> + * The bounds of the range are allowed to be negative.
> + *
> + * @param from the start of the range
> + * @param to the end of the range (inclusive)
> + * @return an unmodifiable list of integers in the specified range
> + * @throws IllegalArgumentException if from > to
> + * @since 4.0
> + */
> + public static List<Integer> range(final int from, final int to) {
> + return ListUtils.unmodifiableList(new RangeList(from, to));
> + }
> +
> + /**
> + * Provides a memory-efficient implementation of a fixed range list.
> + * @since 4.0
> + */
> + private static final class RangeList extends AbstractList<Integer> {
> + private final int from;
> + private final int to;
> +
> + /**
> + * Creates a list of integers with a given range, inclusive.
> + *
> + * @param from the start of the range
> + * @param to the end of the range (inclusive)
> + * @throws IllegalArgumentException if from > to
> + */
> + private RangeList(final int from, final int to) {
> + if (to < from) {
> + throw new IllegalArgumentException("from(" + from + ") >
> to(" + to + ")");
> + }
> +
> + this.from = from;
> + this.to = to;
> + }
> +
> + public int size() {
> + return to - from + 1;
> + }
> +
> + public Integer get(final int index) {
> + final int sz = size();
> + if (index >= sz || index < 0) {
> + throw new IndexOutOfBoundsException("Index: " + index +
> ", Size: " + sz);
> + }
> + return Integer.valueOf(index + from);
> + }
> +
> + public int indexOf(Object o) {
> + if (o instanceof Number) {
+ final int value = ((Number) o).intValue();
>
Why do we cast to Number instead of Integer?
With this implementation the following will fail:
public void testRange() {
List<Integer> range = ListUtils.range(0, 1);
assertFalse(range.contains(Double.valueOf(1.2d)));
}
> + if (value >= from && value <= to) {
> + return value - from;
> + }
> + }
> + return -1;
> + }
> +
> + public int lastIndexOf(Object o) {
> + return indexOf(o);
> + }
> +
> + public boolean contains(Object o) {
> + return indexOf(o) != -1;
> + }
> + }
> }
>
>
>
--
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