Class ResizableDoubleArray
- All Implemented Interfaces:
Serializable
The internal storage array starts with capacity determined by the
initialCapacity
property, which can be set by the constructor.
The default initial capacity is 16. Adding elements using
addElement(double)
appends elements to the end of the array.
When there are no open entries at the end of the internal storage array,
the array is expanded. The size of the expanded array depends on the
expansionMode
and expansionFactor
properties.
The expansionMode
determines whether the size of the array is
multiplied by the expansionFactor
(ResizableDoubleArray.ExpansionMode.MULTIPLICATIVE
) or if the expansion is additive
(ResizableDoubleArray.ExpansionMode.ADDITIVE
-- expansionFactor
storage
locations added).
The default expansionMode
is MULTIPLICATIVE
and the default
expansionFactor
is 2.
The addElementRolling(double)
method adds a new element to the end
of the internal storage array and adjusts the "usable window" of the
internal array forward by one position (effectively making what was the
second element the first, and so on). Repeated activations of this method
(or activation of discardFrontElements(int)
) will effectively orphan
the storage locations at the beginning of the internal storage array. To
reclaim this storage, each time one of these methods is activated, the size
of the internal storage array is compared to the number of addressable
elements (the numElements
property) and if the difference
is too large, the internal array is contracted to size
numElements + 1
. The determination of when the internal
storage array is "too large" depends on the expansionMode
and
contractionFactor
properties. If the expansionMode
is MULTIPLICATIVE
, contraction is triggered when the
ratio between storage array length and numElements
exceeds
contractionFactor.
If the expansionMode
is ADDITIVE
, the number of excess storage locations
is compared to contractionFactor
.
To avoid cycles of expansions and contractions, the
expansionFactor
must not exceed the contractionFactor
.
Constructors and mutators for both of these properties enforce this
requirement, throwing a MathIllegalArgumentException
if it is
violated.
Note: this class is NOT thread-safe.
- See Also:
-
Nested Class Summary
Modifier and TypeClassDescriptionstatic enum
Specification of expansion algorithm. -
Constructor Summary
ConstructorDescriptionCreates an instance with default properties.ResizableDoubleArray
(double[] initialArray) Creates an instance from an existingdouble[]
with the initial capacity and numElements corresponding to the size of the supplieddouble[]
array.ResizableDoubleArray
(int initialCapacity) Creates an instance with the specified initial capacity.ResizableDoubleArray
(int initialCapacity, double expansionFactor) Creates an instance with the specified initial capacity and expansion factor.ResizableDoubleArray
(int initialCapacity, double expansionFactor, double contractionCriterion) Creates an instance with the specified initial capacity, expansion factor, and contraction criteria.ResizableDoubleArray
(int initialCapacity, double expansionFactor, double contractionCriterion, ResizableDoubleArray.ExpansionMode expansionMode, double... data) Creates an instance with the specified properties.ResizableDoubleArray
(ResizableDoubleArray original) Copy constructor. -
Method Summary
Modifier and TypeMethodDescriptionvoid
addElement
(double value) Adds an element to the end of this expandable array.double
addElementRolling
(double value) Adds an element to the end of the array and removes the first element in the array.void
addElements
(double[] values) Adds several element to the end of this expandable array.protected void
checkContractExpand
(double contraction, double expansion) Checks the expansion factor and the contraction criterion and raises an exception if the contraction criterion is smaller than the expansion criterion.void
clear()
Clear the array contents, resetting the number of elements to zero.double
Performs an operation on the addressable elements of the array.void
contract()
Contracts the storage array to the (size of the element set) + 1 - to avoid a zero length array.copy()
Returns a copy of the ResizableDoubleArray.void
discardFrontElements
(int i) Discards thei
initial elements of the array.void
discardMostRecentElements
(int i) Discards thei
last elements of the array.boolean
Returns true iff object is a ResizableDoubleArray with the same properties as this and an identical internal storage array.protected void
expand()
Expands the internal storage array using the expansion factor.protected double[]
Provides direct access to the internal storage array.int
Gets the currently allocated size of the internal data structure used for storing elements.double
The contraction criterion defines when the internal array will contract to store only the number of elements in the element array.double
getElement
(int index) Returns the element at the specified index.double[]
Returns a double array containing the elements of this ResizableArray.double
The expansion factor controls the size of a new array when an array needs to be expanded.The expansion mode determines whether the internal storage array grows additively or multiplicatively when it is expanded.int
Returns the number of elements currently in the array.protected int
Returns the "start index" of the internal array.int
hashCode()
Returns a hash code consistent with equals.void
setElement
(int index, double value) Sets the element at the specified index.void
setNumElements
(int i) This function allows you to control the number of elements contained in this array, and can be used to "throw out" the last n values in an array.double
substituteMostRecentElement
(double value) Substitutesvalue
for the most recently added value.
-
Constructor Details
-
ResizableDoubleArray
public ResizableDoubleArray()Creates an instance with default properties.initialCapacity = 16
expansionMode = MULTIPLICATIVE
expansionFactor = 2.0
contractionCriterion = 2.5
-
ResizableDoubleArray
Creates an instance with the specified initial capacity.Other properties take default values:
expansionMode = MULTIPLICATIVE
expansionFactor = 2.0
contractionCriterion = 2.5
- Parameters:
initialCapacity
- Initial size of the internal storage array.- Throws:
MathIllegalArgumentException
- ifinitialCapacity <= 0
.
-
ResizableDoubleArray
public ResizableDoubleArray(double[] initialArray) Creates an instance from an existingdouble[]
with the initial capacity and numElements corresponding to the size of the supplieddouble[]
array.If the supplied array is null, a new empty array with the default initial capacity will be created. The input array is copied, not referenced. Other properties take default values:
expansionMode = MULTIPLICATIVE
expansionFactor = 2.0
contractionCriterion = 2.5
- Parameters:
initialArray
- initial array
-
ResizableDoubleArray
public ResizableDoubleArray(int initialCapacity, double expansionFactor) throws MathIllegalArgumentException Creates an instance with the specified initial capacity and expansion factor.The remaining properties take default values:
expansionMode = MULTIPLICATIVE
contractionCriterion = 0.5 + expansionFactor
Throws MathIllegalArgumentException if the following conditions are not met:
initialCapacity > 0
expansionFactor > 1
- Parameters:
initialCapacity
- Initial size of the internal storage array.expansionFactor
- The array will be expanded based on this parameter.- Throws:
MathIllegalArgumentException
- if parameters are not valid.
-
ResizableDoubleArray
public ResizableDoubleArray(int initialCapacity, double expansionFactor, double contractionCriterion) throws MathIllegalArgumentException Creates an instance with the specified initial capacity, expansion factor, and contraction criteria.The expansion mode will default to
MULTIPLICATIVE
.Throws MathIllegalArgumentException if the following conditions are not met:
initialCapacity > 0
expansionFactor > 1
contractionCriterion >= expansionFactor
- Parameters:
initialCapacity
- Initial size of the internal storage array.expansionFactor
- The array will be expanded based on this parameter.contractionCriterion
- Contraction criterion.- Throws:
MathIllegalArgumentException
- if the parameters are not valid.
-
ResizableDoubleArray
public ResizableDoubleArray(int initialCapacity, double expansionFactor, double contractionCriterion, ResizableDoubleArray.ExpansionMode expansionMode, double... data) throws MathIllegalArgumentException Creates an instance with the specified properties.
Throws MathIllegalArgumentException if the following conditions are not met:initialCapacity > 0
expansionFactor > 1
contractionCriterion >= expansionFactor
- Parameters:
initialCapacity
- Initial size of the internal storage array.expansionFactor
- The array will be expanded based on this parameter.contractionCriterion
- Contraction criteria.expansionMode
- Expansion mode.data
- Initial contents of the array.- Throws:
MathIllegalArgumentException
- if the parameters are not valid.NullArgumentException
- if expansionMode is null
-
ResizableDoubleArray
Copy constructor.Creates a new ResizableDoubleArray that is a deep, fresh copy of the original. Original may not be null; otherwise a
NullArgumentException
is thrown.- Parameters:
original
- array to copy- Throws:
NullArgumentException
- if original is null
-
-
Method Details
-
addElement
public void addElement(double value) Adds an element to the end of this expandable array.- Parameters:
value
- Value to be added to end of array.
-
addElements
public void addElements(double[] values) Adds several element to the end of this expandable array.- Parameters:
values
- Values to be added to end of array.
-
addElementRolling
public double addElementRolling(double value) Adds an element to the end of the array and removes the first element in the array. Returns the discarded first element.The effect is similar to a push operation in a FIFO queue.
Example: If the array contains the elements 1, 2, 3, 4 (in that order) and addElementRolling(5) is invoked, the result is an array containing the entries 2, 3, 4, 5 and the value returned is 1.
- Parameters:
value
- Value to be added to the array.- Returns:
- the value which has been discarded or "pushed" out of the array by this rolling insert.
-
substituteMostRecentElement
Substitutesvalue
for the most recently added value.Returns the value that has been replaced. If the array is empty (i.e. if
numElements
is zero), an MathIllegalStateException is thrown.- Parameters:
value
- New value to substitute for the most recently added value- Returns:
- the value that has been replaced in the array.
- Throws:
MathIllegalStateException
- if the array is empty
-
checkContractExpand
protected void checkContractExpand(double contraction, double expansion) throws MathIllegalArgumentException Checks the expansion factor and the contraction criterion and raises an exception if the contraction criterion is smaller than the expansion criterion.- Parameters:
contraction
- Criterion to be checked.expansion
- Factor to be checked.- Throws:
MathIllegalArgumentException
- ifcontraction < expansion
.MathIllegalArgumentException
- ifcontraction <= 1
.MathIllegalArgumentException
- ifexpansion <= 1
.
-
clear
public void clear()Clear the array contents, resetting the number of elements to zero. -
contract
public void contract()Contracts the storage array to the (size of the element set) + 1 - to avoid a zero length array. This function also resets the startIndex to zero. -
discardFrontElements
Discards thei
initial elements of the array.For example, if the array contains the elements 1,2,3,4, invoking
discardFrontElements(2)
will cause the first two elements to be discarded, leaving 3,4 in the array.- Parameters:
i
- the number of elements to discard from the front of the array- Throws:
MathIllegalArgumentException
- if i is greater than numElements.
-
discardMostRecentElements
Discards thei
last elements of the array.For example, if the array contains the elements 1,2,3,4, invoking
discardMostRecentElements(2)
will cause the last two elements to be discarded, leaving 1,2 in the array.- Parameters:
i
- the number of elements to discard from the end of the array- Throws:
MathIllegalArgumentException
- if i is greater than numElements.
-
expand
protected void expand()Expands the internal storage array using the expansion factor.If
expansionMode
is set to MULTIPLICATIVE, the new array size will beinternalArray.length * expansionFactor
. IfexpansionMode
is set to ADDITIVE, the length after expansion will beinternalArray.length + expansionFactor
. -
getContractionCriterion
public double getContractionCriterion()The contraction criterion defines when the internal array will contract to store only the number of elements in the element array.If the
expansionMode
isMULTIPLICATIVE
, contraction is triggered when the ratio between storage array length andnumElements
exceedscontractionFactor
. If theexpansionMode
isADDITIVE
, the number of excess storage locations is compared tocontractionFactor
.- Returns:
- the contraction criterion used to reclaim memory.
-
getElement
public double getElement(int index) Returns the element at the specified index.- Parameters:
index
- index to fetch a value from- Returns:
- value stored at the specified index
- Throws:
ArrayIndexOutOfBoundsException
- ifindex
is less than zero or is greater thangetNumElements() - 1
.
-
getElements
public double[] getElements()Returns a double array containing the elements of this ResizableArray.This method returns a copy, not a reference to the underlying array, so that changes made to the returned array have no effect on this ResizableArray.
- Returns:
- the double array.
-
getExpansionFactor
public double getExpansionFactor()The expansion factor controls the size of a new array when an array needs to be expanded.The
expansionMode
determines whether the size of the array is multiplied by theexpansionFactor
(MULTIPLICATIVE) or if the expansion is additive (ADDITIVE --expansionFactor
storage locations added). The defaultexpansionMode
is MULTIPLICATIVE and the defaultexpansionFactor
is 2.0.- Returns:
- the expansion factor of this expandable double array
-
getExpansionMode
The expansion mode determines whether the internal storage array grows additively or multiplicatively when it is expanded.- Returns:
- the expansion mode.
-
getCapacity
public int getCapacity()Gets the currently allocated size of the internal data structure used for storing elements. This is not to be confused withthe number of elements actually stored
.- Returns:
- the length of the internal array.
-
getNumElements
public int getNumElements()Returns the number of elements currently in the array. Please note that this is different from the length of the internal storage array.- Returns:
- the number of elements.
-
getArrayRef
protected double[] getArrayRef()Provides direct access to the internal storage array. Please note that this method returns a reference to this object's storage array, not a copy.To correctly address elements of the array, the "start index" is required (available via the
getStartIndex
method.This method should only be used to avoid copying the internal array. The returned value must be used for reading only; other uses could lead to this object becoming inconsistent.
The
getElements()
method has no such limitation since it returns a copy of this array's addressable elements.- Returns:
- the internal storage array used by this object.
-
getStartIndex
protected int getStartIndex()Returns the "start index" of the internal array. This index is the position of the first addressable element in the internal storage array.The addressable elements in the array are at indices contained in the interval [
getStartIndex()
,getStartIndex()
+getNumElements()
- 1].- Returns:
- the start index.
-
compute
Performs an operation on the addressable elements of the array.- Parameters:
f
- Function to be applied on this array.- Returns:
- the result.
-
setElement
public void setElement(int index, double value) Sets the element at the specified index.If the specified index is greater than
getNumElements() - 1
, thenumElements
property is increased toindex +1
and additional storage is allocated (if necessary) for the new element and all (uninitialized) elements between the new element and the previous end of the array).- Parameters:
index
- index to store a value invalue
- value to store at the specified index- Throws:
ArrayIndexOutOfBoundsException
- ifindex < 0
.
-
setNumElements
This function allows you to control the number of elements contained in this array, and can be used to "throw out" the last n values in an array. This function will also expand the internal array as needed.- Parameters:
i
- a new number of elements- Throws:
MathIllegalArgumentException
- ifi
is negative.
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copy
Returns a copy of the ResizableDoubleArray. Does not contract before the copy, so the returned object is an exact copy of this.- Returns:
- a new ResizableDoubleArray with the same data and configuration properties as this
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equals
Returns true iff object is a ResizableDoubleArray with the same properties as this and an identical internal storage array. -
hashCode
public int hashCode()Returns a hash code consistent with equals.
-