de.javagl.sampling.list

Class ListSlidingWindows

java.lang.Object

de.javagl.sampling.list.ListSlidingWindows

public class ListSlidingWindows
extends Object

Methods to create streams of lists that are sliding window views on other lists.

Method Summary

Modifier and Type	Method and Description
static <T> Stream<List<T>>	createClosedSlidingWindow(List<? extends T> input, int windowSize, int stepSize) Create a stream that contains lists that are a sliding window over the given input list.
static <T> Stream<List<T>>	createSlidingWindow(List<? extends T> input, int windowSize, int start, int maxEnd, int stepSize) Create a stream that contains lists that are a sliding window over the given input list.

Methods inherited from class java.lang.Object

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

Method Detail

createClosedSlidingWindow

public static <T> Stream<List<T>> createClosedSlidingWindow(List<? extends T> input,
                                                            int windowSize,
                                                            int stepSize)

Create a stream that contains lists that are a sliding window over the given input list. The lists will be returned in form of unmodifiable lists.

The lists of the resulting stream will cover the closed range of the given input list. This means that the first result starts at the beginning of the list, and the last result at most includes the last element of the list.

This implies that all returned lists will have exactly windowSize elements. If the window size is larger than the input list, then the stream will be empty.

Examples:

For a window size of 5 and a step size of 2, the method will behave as follows:

 input   :             [0, 1, 2, 3, 4, 5, 6, 7 ]
 output  : 
                       [0, 1, 2, 3, 4 ]
                             [2, 3, 4, 5, 6 ]
 

 input   :             [0, 1, 2, 3, 4, 5, 6, 7, 8 ]
 output  : 
                       [0, 1, 2, 3, 4 ]
                             [2, 3, 4, 5, 6 ]
                                   [4, 5, 6, 7, 8 ]
 

If the given list is modified after the stream has been created, the behavior of the stream is unspecified.

If the given list is modified after the windows have been obtained from the stream, the behavior of the windows is unspecified.

Type Parameters:

T - The element type

Parameters:

input - The input list

windowSize - The window size

stepSize - The step size

Returns:

The stream

Throws:

IllegalArgumentException - If the window size or the step size is not positive

createSlidingWindow

public static <T> Stream<List<T>> createSlidingWindow(List<? extends T> input,
                                                      int windowSize,
                                                      int start,
                                                      int maxEnd,
                                                      int stepSize)

Create a stream that contains lists that are a sliding window over the given input list. The lists will be returned in form of unmodifiable lists.

The sliding windows will cover the given index range. These indices will be clamped to [0, input.size()).

The first element of the first window list will be the element that is located at the start index of the given list. The last window will contain no element that is located at an index of the input list that is equal to or greater than the maxEnd index.

Note that this method does very few checks on the given parameters. It is possible to call it with parameters that will not make sense in a real application, for example, using a window size or a step size that is larger than the list, or starting the computations at a start index that is smaller than -windowSize. (The latter will simply cause the first lists to be empty.)
If the given list is modified after the stream has been created, the behavior of the stream is unspecified.

If the given list is modified after the windows have been obtained from the stream, the behavior of the windows is unspecified.

Type Parameters:

T - The element type

Parameters:

input - The input list

windowSize - The window size

start - The start index, inclusive

maxEnd - The maximum end index, exclusive

stepSize - The step size

Returns:

The stream

Throws:

IllegalArgumentException - If the window size or the step size is not positive