public virtual void TestFilter()
{
IList <string> values = Arrays.AsList("a", "HI", "tHere", "YO");
IEnumerator <string> iterator = Iterables.Filter(values, null).GetEnumerator();
NUnit.Framework.Assert.IsTrue(iterator.MoveNext());
NUnit.Framework.Assert.AreEqual(iterator.Current, "HI");
NUnit.Framework.Assert.AreEqual(iterator.Current, "YO");
NUnit.Framework.Assert.IsFalse(iterator.MoveNext());
}
/// <summary>Sample k items uniformly from an Iterable of size n (without replacement).</summary>
/// <param name="items">The items from which to sample.</param>
/// <param name="n">The total number of items in the Iterable.</param>
/// <param name="k">The number of items to sample.</param>
/// <param name="random">The random number generator.</param>
/// <returns>An Iterable of k items, chosen randomly from the original n items.</returns>
public static IEnumerable <T> Sample <T>(IEnumerable <T> items, int n, int k, Random random)
{
// assemble a list of all indexes
IList <int> indexes = new List <int>();
for (int i = 0; i < n; ++i)
{
indexes.Add(i);
}
// shuffle the indexes and select the first k
Java.Util.Collections.Shuffle(indexes, random);
ICollection <int> indexSet = Generics.NewHashSet(indexes.SubList(0, k));
// filter down to only the items at the selected indexes
return(Iterables.Filter(items, new _IPredicate_614(indexSet)));
}
