jsat.utils

Class ListUtils

java.lang.Object

jsat.utils.ListUtils

public class ListUtils
extends Object

Author:

Edward Raff

Method Summary

Modifier and Type	Method and Description
static void	addRange(Collection<Integer> c, int start, int to, int step) Adds values into the given collection using integer in the specified range and step size.
static <T> List<T>	collectFutures(Collection<Future<T>> futures) Collects all future values in a collection into a list, and returns said list.
static <T> List<T>	mergedView(List<T> left, List<T> right) Returns a new unmodifiable view that is the merging of two lists
static <T> void	randomSample(Collection<T> source, Collection<T> dest, int samples, Random rand) Obtains a random sample without replacement from a source collection and places it in the destination collection.
static <T> void	randomSample(List<T> source, List<T> dest, int samples) Obtains a random sample without replacement from a source list and places it in the destination list.
static <T> void	randomSample(List<T> source, List<T> dest, int samples, Random rand) Obtains a random sample without replacement from a source list and places it in the destination list.
static <T> List<List<T>>	splitList(List<T> source, int count) This method takes a list and breaks it into count lists backed by the original list, with elements being equally spaced among the lists.
static void	swap(List list, int i, int j) Swaps the values in the list at the given positions

Methods inherited from class java.lang.Object

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

Method Detail

splitList

public static <T> List<List<T>> splitList(List<T> source,
                                          int count)

This method takes a list and breaks it into count lists backed by the original list, with elements being equally spaced among the lists. The lists will be returned in order of the consecutive values they represent in the source list.

NOTE: Because the implementation uses List.subList(int, int), changes to the returned lists will be reflected in the source list.

Type Parameters:

T - the type contained in the list

Parameters:

source - the source list that will be used to back the count lists

count - the number of lists to partition the source into.

Returns:

a lists of lists, each of with the same size with at most a difference of 1.

mergedView

public static <T> List<T> mergedView(List<T> left,
                                     List<T> right)

Returns a new unmodifiable view that is the merging of two lists

Type Parameters:

T - the type the lists hold

Parameters:

left - the left portion of the merged view

right - the right portion of the merged view

Returns:

a list view that contains bot the left and right lists

swap

public static void swap(List list,
                        int i,
                        int j)

Swaps the values in the list at the given positions

Parameters:

list - the list to perform the swap in

i - the first position to swap

j - the second position to swap

collectFutures

public static <T> List<T> collectFutures(Collection<Future<T>> futures)
                                  throws ExecutionException,
                                         InterruptedException

Collects all future values in a collection into a list, and returns said list. This method will block until all future objects are collected.

Type Parameters:

T - the type of future object

Parameters:

futures - the collection of future objects

Returns:

a list containing the object from the future.

Throws:

ExecutionException

InterruptedException

addRange

public static void addRange(Collection<Integer> c,
                            int start,
                            int to,
                            int step)

Adds values into the given collection using integer in the specified range and step size. If the start value is greater or equal to the to value, nothing will be added to the collection.

Parameters:

c - the collection to add to

start - the first value to add, inclusive

to - the last value to add, exclusive

step - the step size.

Throws:

RuntimeException - if the step size is zero or negative.

randomSample

public static <T> void randomSample(List<T> source,
                                    List<T> dest,
                                    int samples,
                                    Random rand)

Obtains a random sample without replacement from a source list and places it in the destination list. This is done without modifying the source list.

Type Parameters:

T - the list content type involved

Parameters:

source - the source of values to randomly sample from

dest - the list to store the random samples in. The list does not need to be empty for the sampling to work correctly

samples - the number of samples to select from the source

rand - the source of randomness for the sampling

Throws:

IllegalArgumentException - if the sample size is not positive or l arger than the source population.

randomSample

public static <T> void randomSample(Collection<T> source,
                                    Collection<T> dest,
                                    int samples,
                                    Random rand)

Obtains a random sample without replacement from a source collection and places it in the destination collection. This is done without modifying the source collection.
This random sampling is oblivious to failures to add to a collection that may occur, such as if the collection is a Set

Type Parameters:

T - the list content type involved

Parameters:

source - the source of values to randomly sample from

dest - the collection to store the random samples in. It does not need to be empty for the sampling to work correctly

samples - the number of samples to select from the source

rand - the source of randomness for the sampling

Throws:

IllegalArgumentException - if the sample size is not positive or l arger than the source population.

randomSample

public static <T> void randomSample(List<T> source,
                                    List<T> dest,
                                    int samples)

Obtains a random sample without replacement from a source list and places it in the destination list. This is done without modifying the source list.

Type Parameters:

T - the list content type involved

Parameters:

source - the source of values to randomly sample from

dest - the list to store the random samples in. The list does not need to be empty for the sampling to work correctly

samples - the number of samples to select from the source

Throws:

IllegalArgumentException - if the sample size is not positive or l arger than the source population.