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).

Compatibility

Public

Method Summary

Modifier and Type	Method and Description
static <E> FastCollection<E>	emptyFastCollection() Deprecated. Just use a standard empty collection.
static <E> Iterable<E>	fast(Iterable<E> iter) Deprecated. Fast iteration has gone away. This method now does nothing.
static <E> FastIterable<E>	fastFilterAndLimit(Iterable<E> iter, Predicate<? super E> pred, int limit) Deprecated. Fast iteration has gone away.
static IntList	interval(int from, int to) Create an IntList that contains all numbers in a specified interval.
static <E> 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

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

Deprecated. Fast iteration has gone away. This method now does nothing.

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.

fastFilterAndLimit

@Deprecated
public static <E> FastIterable<E> fastFilterAndLimit(Iterable<E> iter,
                                                                 Predicate<? super E> pred,
                                                                 int limit)

Deprecated. Fast iteration has gone away.

Fast-aware filter-and-limit operation, filtering an iterable. If the underlying iterable does not support fast iteration, then the returned iterable's fast iteration will fall back to ordinary iteration.

Type Parameters:

E - The type of data in the iterable.

Parameters:

iter - The iterable to filter and limit.

pred - The predicate for filtering.

limit - The maximum number of items to return (negative for unlimited).

Returns:

A fast iterable filtering and limiting.

objectCollection

public static <E> 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 obj n times.

emptyFastCollection

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

Deprecated. Just use a standard empty collection.

Create an empty, immutable fast collection.

Type Parameters:

E - The type of fast collection.

Returns:

An empty fast collection.

interval

public static 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).