net.librec.util

Class Lists

java.lang.Object

net.librec.util.Lists

public class Lists
extends java.lang.Object

This class is for the operations of arrays or collections

Author:

Felix and Keqiang Wang

Constructor Summary

Constructors

Constructor and Description
Lists()

Method Summary

Methods

Modifier and Type	Method and Description
static <T> java.util.List<T>	except(java.util.List<T> list1, java.util.List<T> list2) Note: if you need to operate on the original list, it's better to use the method "retainAll" or "removeAll"
static <T> int	exceptSize(java.util.List<T> list1, java.util.List<T> list2)
static <E> int	initSize(java.util.Collection<E> collection)
static int	initSize(int capacity)
static <T> java.util.List<T>	intersect(java.util.List<T> list1, java.util.List<T> list2)
static <T> boolean	isEmpty(java.util.List<T> ts)
static <T> int	overlapSize(java.util.List<T> list1, java.util.List<T> list2)
static void	shaffle(double[] data) Rearrange the elements of a double array in random order.
static void	shaffle(int[] data) Rearrange the elements of a int array in random order.
static <T> void	shaffle(java.util.List<T> data) Shuffle the elements of a List.
static <K,V extends java.lang.Comparable<? super V>> void	sortItemEntryList(java.util.List<ItemEntry<K,V>> data) sort a map object: List<ItemEntry<K, V extends Comparable<? extends V>>
static <K,V extends java.lang.Comparable<? super V>> void	sortItemEntryList(java.util.List<ItemEntry<K,V>> data, boolean inverse) sort a list of objects: List<ItemEntry<K, V extends Comparable<? extends V>>
static <K,V extends java.lang.Comparable<? super V>> java.util.List<ItemEntry<K,V>>	sortItemEntryListTopK(java.util.List<ItemEntry<K,V>> data, boolean inverse, int k) sort a list of objects: List<ItemEntry<K, V extends Comparable<? extends V>>
static <K,V extends java.lang.Comparable<? super V>> java.util.List<ItemEntry<K,V>>	sortItemEntryListTopK(java.util.List<ItemEntry<K,V>> data, int k) sort a list object: List<ItemEntry<K, V extends Comparable<? extends V>>
static <K,V extends java.lang.Comparable<? super V>> void	sortList(java.util.List<java.util.Map.Entry<K,V>> data) sort a map object: List<Map.Entry<K, V extends Comparable<? extends V>>
static <K,V extends java.lang.Comparable<? super V>> void	sortList(java.util.List<java.util.Map.Entry<K,V>> data, boolean inverse) sort a list of objects: List<Map.Entry<K, V extends Comparable<? extends V>>
static <K,V extends java.lang.Comparable<? super V>> java.util.List<java.util.Map.Entry<K,V>>	sortList(java.util.List<java.util.Map.Entry<K,V>> data, int k) sort a list object: List<Map.Entry<K, V extends Comparable<? extends V>>
static <K,V extends java.lang.Comparable<? super V>> java.util.List<java.util.Map.Entry<K,V>>	sortListTopK(java.util.List<java.util.Map.Entry<K,V>> data, boolean inverse, int k) sort a list of objects: List<Map.Entry<K, V extends Comparable<? extends V>>
static <K,V extends java.lang.Comparable<? super V>> java.util.List<java.util.Map.Entry<K,V>>	sortMap(java.util.Map<K,V> data) sort a map object: Map<K, V extends Comparable<? extends V>
static <K,V extends java.lang.Comparable<? super V>> java.util.List<java.util.Map.Entry<K,V>>	sortMap(java.util.Map<K,V> data, boolean inverse) sort an Map<K, V extends Comparable<? extends V> map object
static <T> java.util.List<T>	subset(java.util.List<T> data, int n)
static double[]	toArray(java.util.Collection<? extends java.lang.Number> data) Turn a collection of data into an double array
static java.util.List<java.lang.Double>	toList(double[] data) Turn an double array into a List<Double> object
static java.util.List<java.lang.Integer>	toList(int[] data) Convert int array to int list

Methods inherited from class java.lang.Object

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

Constructor Detail

Lists

public Lists()

Method Detail

initSize

public static int initSize(int capacity)

Parameters:

capacity - a given capacity

Returns:

the proper initial size for a target given capacity, based on the default "load factor=0.7"

initSize

public static <E> int initSize(java.util.Collection<E> collection)

shaffle

public static void shaffle(int[] data)

Rearrange the elements of a int array in random order.

Parameters:

data - a int array

shaffle

public static void shaffle(double[] data)

Rearrange the elements of a double array in random order.

Parameters:

data - a double array

shaffle

public static <T> void shaffle(java.util.List<T> data)

Shuffle the elements of a List.

Type Parameters:

T - type parameter

Parameters:

data - a List

subset

public static <T> java.util.List<T> subset(java.util.List<T> data,
                           int n)

Type Parameters:

T - type parameter

Parameters:

data - a list

n - top-n number

Returns:

the top-n subset of list data

intersect

public static <T> java.util.List<T> intersect(java.util.List<T> list1,
                              java.util.List<T> list2)

Type Parameters:

T - type parameter

Parameters:

list1 - list 1

list2 - list 2

Returns:

a new list of the intersection of two lists: list1 and list2

overlapSize

public static <T> int overlapSize(java.util.List<T> list1,
                  java.util.List<T> list2)

Type Parameters:

T - type parameter

Parameters:

list1 - list 1

list2 - list 2

Returns:

the number of common items of two lists: list1 and list2

except

public static <T> java.util.List<T> except(java.util.List<T> list1,
                           java.util.List<T> list2)

Note: if you need to operate on the original list, it's better to use the method "retainAll" or "removeAll"

Type Parameters:

T - type parameter

Parameters:

list1 - list 1

list2 - list 2

Returns:

a new list with the exception of two lists: list1 and list2

exceptSize

public static <T> int exceptSize(java.util.List<T> list1,
                 java.util.List<T> list2)

Type Parameters:

T - type parameter

Parameters:

list1 - list 1

list2 - list 2

Returns:

the number of elements in the first list but not in the second list

isEmpty

public static <T> boolean isEmpty(java.util.List<T> ts)

Type Parameters:

T - type parameter

Parameters:

ts - a list

Returns:

whether list is empty: null or no elements insides

toArray

public static double[] toArray(java.util.Collection<? extends java.lang.Number> data)

Turn a collection of data into an double array

Parameters:

data - a collection of data

Returns:

an double array

toList

public static java.util.List<java.lang.Double> toList(double[] data)

Turn an double array into a List<Double> object

Parameters:

data - an double array

Returns:

a List<Double> object

toList

public static java.util.List<java.lang.Integer> toList(int[] data)

Convert int array to int list

Parameters:

data - an double array

Returns:

int list

sortMap

public static <K,V extends java.lang.Comparable<? super V>> java.util.List<java.util.Map.Entry<K,V>> sortMap(java.util.Map<K,V> data,
                                                                                             boolean inverse)

sort an Map<K, V extends Comparable<? extends V> map object

Remark: note that this method may be memory-consuming as it needs to make an ArrayList copy of input Map data. Instead, we suggest to store original data in List<Map.Entry<K,V>> and use sortList() method to avoid object copying.

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - map data

inverse - descending if true; otherwise ascending

Returns:

a sorted list

sortMap

public static <K,V extends java.lang.Comparable<? super V>> java.util.List<java.util.Map.Entry<K,V>> sortMap(java.util.Map<K,V> data)

sort a map object: Map<K, V extends Comparable<? extends V>

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - map data

Returns:

an ascending sorted list

sortList

public static <K,V extends java.lang.Comparable<? super V>> void sortList(java.util.List<java.util.Map.Entry<K,V>> data,
                                                          boolean inverse)

sort a list of objects: List<Map.Entry<K, V extends Comparable<? extends V>>

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - map data

inverse - descending if true; otherwise ascending

sortList

public static <K,V extends java.lang.Comparable<? super V>> void sortList(java.util.List<java.util.Map.Entry<K,V>> data)

sort a map object: List<Map.Entry<K, V extends Comparable<? extends V>>

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - map data

sortListTopK

public static <K,V extends java.lang.Comparable<? super V>> java.util.List<java.util.Map.Entry<K,V>> sortListTopK(java.util.List<java.util.Map.Entry<K,V>> data,
                                                                                                  boolean inverse,
                                                                                                  int k)

sort a list of objects: List<Map.Entry<K, V extends Comparable<? extends V>>

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - map data

inverse - descending if true; otherwise ascending

k - k

Returns:

a topk sorted list 10000 users, 10000 items, top 30, 809ms vs 18654ms 10000 users, 10000 items, top 100, 1443ms vs 18654ms 10000 users, 100000 items, top 30, 10.4s vs 323s 10000 users, 100000 items, top 100, 10.8s vs 323s

sortList

public static <K,V extends java.lang.Comparable<? super V>> java.util.List<java.util.Map.Entry<K,V>> sortList(java.util.List<java.util.Map.Entry<K,V>> data,
                                                                                              int k)

sort a list object: List<Map.Entry<K, V extends Comparable<? extends V>>

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - list data

k - k

Returns:

an top k ascending sorted list

sortItemEntryListTopK

public static <K,V extends java.lang.Comparable<? super V>> java.util.List<ItemEntry<K,V>> sortItemEntryListTopK(java.util.List<ItemEntry<K,V>> data,
                                                                                                 boolean inverse,
                                                                                                 int k)

sort a list of objects: List<ItemEntry<K, V extends Comparable<? extends V>>

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - map data

inverse - descending if true; otherwise ascending

k - k

Returns:

a topk sorted list 10000 users, 10000 items, top 30, 809ms vs 18654ms 10000 users, 10000 items, top 100, 1443ms vs 18654ms 10000 users, 100000 items, top 30, 10.4s vs 323s 10000 users, 100000 items, top 100, 10.8s vs 323s

sortItemEntryListTopK

public static <K,V extends java.lang.Comparable<? super V>> java.util.List<ItemEntry<K,V>> sortItemEntryListTopK(java.util.List<ItemEntry<K,V>> data,
                                                                                                 int k)

sort a list object: List<ItemEntry<K, V extends Comparable<? extends V>>

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - list data

k - k

Returns:

an top k ascending sorted list

sortItemEntryList

public static <K,V extends java.lang.Comparable<? super V>> void sortItemEntryList(java.util.List<ItemEntry<K,V>> data,
                                                                   boolean inverse)

sort a list of objects: List<ItemEntry<K, V extends Comparable<? extends V>>

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - map data

inverse - descending if true; otherwise ascending

sortItemEntryList

public static <K,V extends java.lang.Comparable<? super V>> void sortItemEntryList(java.util.List<ItemEntry<K,V>> data)

sort a map object: List<ItemEntry<K, V extends Comparable<? extends V>>

Type Parameters:

K - type parameter

V - type parameter

Parameters:

data - map data