org.grouplens.lenskit.collections

Class CollectionUtils

java.lang.Object

org.grouplens.lenskit.collections.CollectionUtils

public final class CollectionUtils
extends Object

Various helper methods for working with collections (particularly Fastutil collections).

Author:

GroupLens Research

Method Summary

Methods

Modifier and Type	Method and Description
static <E> FastCollection<E>	emptyFastCollection() Create an empty, immutable fast collection.
static <E> Iterable<E>	fast(Iterable<E> iter) Use the fast iterator of an iterable, if available.
static it.unimi.dsi.fastutil.ints.IntList	interval(int from, int to) Create an IntList that contains all numbers in a specified interval.
static <E> it.unimi.dsi.fastutil.objects.ObjectCollection<E>	objectCollection(Collection<E> objects) Wrap a Collection in an ObjectCollection.
static <T> List<T>	repeat(T obj, int n) Return a list that repeats a single object multiple times.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

fast

public static <E> Iterable<E> fast(Iterable<E> iter)

Use the fast iterator of an iterable, if available.

Type Parameters:

E - The type of object to iterate.

Parameters:

iter - An iterable to wrap

Returns:

An iterable using the underlying iterable's fast iterator, if present, to do iteration. Fast iteration is detected by looking for a fastIterator() method, like is present in Long2DoubleMap.FastEntrySet.

objectCollection

public static <E> it.unimi.dsi.fastutil.objects.ObjectCollection<E> objectCollection(Collection<E> objects)

Wrap a Collection in an ObjectCollection.

Type Parameters:

E - The type of objects.

Parameters:

objects - The collection of objects.

Returns:

The collection as an ObjectCollection.

repeat

public static <T> List<T> repeat(T obj,
                 int n)

Return a list that repeats a single object multiple times.

Type Parameters:

T - The type of list elements.

Parameters:

obj - The object.

n - The size of the list.

Returns:

A list containing times.

emptyFastCollection

public static <E> FastCollection<E> emptyFastCollection()

Create an empty, immutable fast collection.

Type Parameters:

E - The type of fast collection.

Returns:

An empty fast collection.

interval

public static it.unimi.dsi.fastutil.ints.IntList interval(int from,
                                          int to)

Create an IntList that contains all numbers in a specified interval.

Parameters:

from - The first number (inclusive)

to - the last number (exclusive).

Returns:

A list containing the integers in the interval [from,to).