java.lang.Object
- org.apache.commons.math.util.ResizableDoubleArray

All Implemented Interfaces:

java.io.Serializable, DoubleArray
```
public class ResizableDoubleArray
extends java.lang.Object
implements DoubleArray, java.io.Serializable
```
A variable length DoubleArray implementation that automatically handles expanding and contracting its internal storage array as elements are added and removed.

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 (MULTIPLICATIVE_MODE) or if the expansion is additive (ADDITIVE_MODE -- expansionFactor storage locations added). The default expansionMode is MULTIPLICATIVE_MODE and the default expansionFactor is 2.0.

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_MODE, contraction is triggered when the ratio between storage array length and numElements exceeds contractionFactor. If the expansionMode is ADDITIVE_MODE, 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 IllegalArgumentException if it is violated.

Version:

$Revision: 1073474 $ $Date: 2011-02-22 20:52:17 +0100 (mar. 22 févr. 2011) $

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type	Field	Description
`static int`	`ADDITIVE_MODE`	additive expansion mode
`protected float`	`contractionCriteria`	The contraction criteria determines when the internal array will be contracted to fit the number of elements contained in the element array + 1.
`protected float`	`expansionFactor`	The expansion factor of the array.
`protected int`	`expansionMode`	Determines whether array expansion by `expansionFactor` is additive or multiplicative.
`protected int`	`initialCapacity`	The initial capacity of the array.
`protected double[]`	`internalArray`	The internal storage array.
`static int`	`MULTIPLICATIVE_MODE`	multiplicative expansion mode
`protected int`	`numElements`	The number of addressable elements in the array.
`protected int`	`startIndex`	The position of the first addressable element in the internal storage array.

Constructor Summary

Constructors
Constructor	Description
`ResizableDoubleArray()`	Create a ResizableArray with default properties.
`ResizableDoubleArray(double[] initialArray)`	Create a ResizableArray from an existing double[] with the initial capacity and numElements corresponding to the size of the supplied double[] array.
`ResizableDoubleArray(int initialCapacity)`	Create a ResizableArray with the specified initial capacity.
`ResizableDoubleArray(int initialCapacity, float expansionFactor)`	Create a ResizableArray with the specified initial capacity and expansion factor.
`ResizableDoubleArray(int initialCapacity, float expansionFactor, float contractionCriteria)`	Create a ResizableArray with the specified initialCapacity, expansionFactor, and contractionCriteria.
`ResizableDoubleArray(int initialCapacity, float expansionFactor, float contractionCriteria, int expansionMode)`	Create a ResizableArray with the specified properties.
`ResizableDoubleArray(ResizableDoubleArray original)`	Copy constructor.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method	Description
`void`	`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(float contraction, float expansion)`	Checks the expansion factor and the contraction criteria and throws an IllegalArgumentException if the contractionCriteria is less than the expansionCriteria
`void`	`clear()`	Clear the array, reset the size to the initialCapacity and the number of elements to zero.
`void`	`contract()`	Contracts the storage array to the (size of the element set) + 1 - to avoid a zero length array.
`ResizableDoubleArray`	`copy()`	Returns a copy of the ResizableDoubleArray.
`static void`	`copy(ResizableDoubleArray source, ResizableDoubleArray dest)`	Copies source to dest, copying the underlying data, so dest is a new, independent copy of source.
`void`	`discardFrontElements(int i)`	Discards the `i initial elements of the array.`
`void`	`discardMostRecentElements(int i)`	Discards the `i last elements of the array.`
`boolean`	`equals(java.lang.Object object)`	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.
`float`	`getContractionCriteria()`	The contraction criteria 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[]`	`getElements()`	Returns a double array containing the elements of this `ResizableArray`.
`float`	`getExpansionFactor()`	The expansion factor controls the size of a new array when an array needs to be expanded.
`int`	`getExpansionMode()`	The `expansionMode` determines whether the internal storage array grows additively (ADDITIVE_MODE) or multiplicatively (MULTIPLICATIVE_MODE) when it is expanded.
`double[]`	`getInternalValues()`	Returns the internal storage array.
`int`	`getNumElements()`	Returns the number of elements currently in the array.
`double[]`	`getValues()`	Deprecated. replaced by `getInternalValues()` as of 2.0
`int`	`hashCode()`	Returns a hash code consistent with equals.
`void`	`setContractionCriteria(float contractionCriteria)`	Sets the contraction criteria for this ExpandContractDoubleArray.
`void`	`setElement(int index, double value)`	Sets the element at the specified index.
`void`	`setExpansionFactor(float expansionFactor)`	Sets the expansionFactor.
`void`	`setExpansionMode(int expansionMode)`	Sets the `expansionMode`.
`protected void`	`setInitialCapacity(int initialCapacity)`	Sets the initial capacity.
`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.
`int`	`start()`	Returns the starting index of the internal array.
`double`	`substituteMostRecentElement(double value)`	Substitutes `value` for the most recently added value.

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - ADDITIVE_MODE
```
public static final int ADDITIVE_MODE
```
    additive expansion mode
    
    See Also:
    
    Constant Field Values
  - MULTIPLICATIVE_MODE
```
public static final int MULTIPLICATIVE_MODE
```
    multiplicative expansion mode
    
    See Also:
    
    Constant Field Values
  - contractionCriteria
```
protected float contractionCriteria
```
    The contraction criteria determines when the internal array will be contracted to fit the number of elements contained in the element array + 1.
  - expansionFactor
```
protected float expansionFactor
```
    The expansion factor of the array. When the array needs to be expanded, the new array size will be internalArray.length * expansionFactor if expansionMode is set to MULTIPLICATIVE_MODE, or internalArray.length + expansionFactor if expansionMode is set to ADDITIVE_MODE.
  - expansionMode
```
protected int expansionMode
```
    Determines whether array expansion by expansionFactor is additive or multiplicative.
  - initialCapacity
```
protected int initialCapacity
```
    The initial capacity of the array. Initial capacity is not exposed as a property as it is only meaningful when passed to a constructor.
  - internalArray
```
protected double[] internalArray
```
    The internal storage array.
  - numElements
```
protected int numElements
```
    The number of addressable elements in the array. Note that this has nothing to do with the length of the internal storage array.
  - startIndex
```
protected int startIndex
```
    The position of the first addressable element in the internal storage array. The addressable elements in the array are internalArray[startIndex],...,internalArray[startIndex + numElements -1]
- Constructor Detail
  - ResizableDoubleArray
```
public ResizableDoubleArray()
```
    Create a ResizableArray with default properties.
    
    initialCapacity = 16
    
    expansionMode = MULTIPLICATIVE_MODE
    
    expansionFactor = 2.5
    
    contractionFactor = 2.0
  - ResizableDoubleArray
```
public ResizableDoubleArray(int initialCapacity)
```
    Create a ResizableArray with the specified initial capacity. Other properties take default values:
    
    expansionMode = MULTIPLICATIVE_MODE
    
    expansionFactor = 2.5
    
    contractionFactor = 2.0
    Parameters:
    
    initialCapacity - The initial size of the internal storage array
    
    Throws:
    
    java.lang.IllegalArgumentException - if initialCapacity is not > 0
  - ResizableDoubleArray
```
public ResizableDoubleArray(double[] initialArray)
```
    Create a ResizableArray from an existing double[] with the initial capacity and numElements corresponding to the size of the supplied double[] 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:
    
    initialCapacity = 16
    
    expansionMode = MULTIPLICATIVE_MODE
    
    expansionFactor = 2.5
    
    contractionFactor = 2.0
    Parameters:
    
    initialArray - initial array
    
    Since:
    
    2.2
  - ResizableDoubleArray
```
public ResizableDoubleArray(int initialCapacity,
                            float expansionFactor)
```
    Create a ResizableArray with the specified initial capacity and expansion factor. The remaining properties take default values:
    
    expansionMode = MULTIPLICATIVE_MODE
    
    contractionFactor = 0.5 + expansionFactor
    
    Throws IllegalArgumentException if the following conditions are not met:
    
    initialCapacity > 0
    
    expansionFactor > 1
    Parameters:
    
    initialCapacity - The initial size of the internal storage array
    
    expansionFactor - the array will be expanded based on this parameter
    
    Throws:
    
    java.lang.IllegalArgumentException - if parameters are not valid
  - ResizableDoubleArray
```
public ResizableDoubleArray(int initialCapacity,
                            float expansionFactor,
                            float contractionCriteria)
```
    Create a ResizableArray with the specified initialCapacity, expansionFactor, and contractionCriteria. The expansionMode will default to MULTIPLICATIVE_MODE.
    
    Throws IllegalArgumentException if the following conditions are not met:
    
    initialCapacity > 0
    
    expansionFactor > 1
    
    contractionFactor >= expansionFactor
    Parameters:
    
    initialCapacity - The initial size of the internal storage array
    
    expansionFactor - the array will be expanded based on this parameter
    
    contractionCriteria - The contraction Criteria.
    
    Throws:
    
    java.lang.IllegalArgumentException - if parameters are not valid
  - ResizableDoubleArray
```
public ResizableDoubleArray(int initialCapacity,
                            float expansionFactor,
                            float contractionCriteria,
                            int expansionMode)
```
    Create a ResizableArray with the specified properties.
    
    Throws IllegalArgumentException if the following conditions are not met:
    
    initialCapacity > 0
    
    expansionFactor > 1
    
    contractionFactor >= expansionFactor
    
    expansionMode in {MULTIPLICATIVE_MODE, ADDITIVE_MODE}
    Parameters:
    
    initialCapacity - the initial size of the internal storage array
    
    expansionFactor - the array will be expanded based on this parameter
    
    contractionCriteria - the contraction Criteria
    
    expansionMode - the expansion mode
    
    Throws:
    
    java.lang.IllegalArgumentException - if parameters are not valid
  - ResizableDoubleArray
```
public ResizableDoubleArray(ResizableDoubleArray original)
```
    Copy constructor. Creates a new ResizableDoubleArray that is a deep, fresh copy of the original. Needs to acquire synchronization lock on original. Original may not be null; otherwise a NullPointerException is thrown.
    
    Parameters:
    
    original - array to copy
    
    Since:
    
    2.0
- Method Detail
  - addElement
```
public void addElement(double value)
```
    Adds an element to the end of this expandable array.
    
    Specified by:
    
    addElement in interface DoubleArray
    
    Parameters:
    
    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 - to be added to end of array
    
    Since:
    
    2.2
  - 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.
    
    Specified by:
    
    addElementRolling in interface DoubleArray
    
    Parameters:
    
    value - the 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
```
public double substituteMostRecentElement(double value)
```
    Substitutes value for the most recently added value. Returns the value that has been replaced. If the array is empty (i.e. if numElements is zero), a MathRuntimeException is thrown.
    
    Parameters:
    
    value - new value to substitute for the most recently added value
    
    Returns:
    
    value that has been replaced in the array
    
    Since:
    
    2.0
  - checkContractExpand
```
protected void checkContractExpand(float contraction,
                                   float expansion)
```
    Checks the expansion factor and the contraction criteria and throws an IllegalArgumentException if the contractionCriteria is less than the expansionCriteria
    
    Parameters:
    
    expansion - factor to be checked
    
    contraction - criteria to be checked
    
    Throws:
    
    java.lang.IllegalArgumentException - if the contractionCriteria is less than the expansionCriteria.
  - clear
```
public void clear()
```
    Clear the array, reset the size to the initialCapacity and the number of elements to zero.
    
    Specified by:
    
    clear in interface DoubleArray
  - 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
```
public void discardFrontElements(int i)
```
    Discards the i 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. Throws illegalArgumentException if i exceeds numElements.
    Parameters: i - the number of elements to discard from the front of the array Throws: java.lang.IllegalArgumentException - if i is greater than numElements. Since: 2.0
  discardMostRecentElements public void discardMostRecentElements(int i) Discards the i 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. Throws illegalArgumentException if i exceeds numElements. Parameters: i - the number of elements to discard from the end of the array Throws: java.lang.IllegalArgumentException - if i is greater than numElements. Since: 2.0 expand protected void expand() Expands the internal storage array using the expansion factor. if expansionMode is set to MULTIPLICATIVE_MODE, the new array size will be internalArray.length * expansionFactor. If expansionMode is set to ADDITIVE_MODE, the length after expansion will be internalArray.length + expansionFactor getContractionCriteria public float getContractionCriteria() The contraction criteria defines when the internal array will contract to store only the number of elements in the element array. If the expansionMode is MULTIPLICATIVE_MODE, contraction is triggered when the ratio between storage array length and numElements exceeds contractionFactor. If the expansionMode is ADDITIVE_MODE, the number of excess storage locations is compared to contractionFactor. Returns: the contraction criteria used to reclaim memory. getElement public double getElement(int index) Returns the element at the specified index Specified by: getElement in interface DoubleArray Parameters: index - index to fetch a value from Returns: value stored at the specified index Throws: java.lang.ArrayIndexOutOfBoundsException - if index is less than zero or is greater than getNumElements() - 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. Specified by: getElements in interface DoubleArray Returns: the double array. getExpansionFactor public float 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 the expansionFactor (MULTIPLICATIVE_MODE) or if the expansion is additive (ADDITIVE_MODE -- expansionFactor storage locations added). The default expansionMode is MULTIPLICATIVE_MODE and the default expansionFactor is 2.0. Returns: the expansion factor of this expandable double array getExpansionMode public int getExpansionMode() The expansionMode determines whether the internal storage array grows additively (ADDITIVE_MODE) or multiplicatively (MULTIPLICATIVE_MODE) when it is expanded. Returns: Returns the expansionMode. 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. Specified by: getNumElements in interface DoubleArray Returns: number of elements getValues @Deprecated public double[] getValues() Deprecated. replaced by getInternalValues() as of 2.0 Returns the internal storage array. Note that this method returns a reference to the internal storage array, not a copy, and to correctly address elements of the array, the startIndex is required (available via the start() method). This method should only be used in cases where copying the internal array is not practical. The getElements() method should be used in all other cases. Returns: the internal storage array used by this object getInternalValues public double[] getInternalValues() Returns the internal storage array. Note that this method returns a reference to the internal storage array, not a copy, and to correctly address elements of the array, the startIndex is required (available via the start() method). This method should only be used in cases where copying the internal array is not practical. The getElements() method should be used in all other cases. Returns: the internal storage array used by this object Since: 2.0 setContractionCriteria public void setContractionCriteria(float contractionCriteria) Sets the contraction criteria for this ExpandContractDoubleArray. Parameters: contractionCriteria - contraction criteria setElement public void setElement(int index, double value) Sets the element at the specified index. If the specified index is greater than getNumElements() - 1, the numElements property is increased to index +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). Specified by: setElement in interface DoubleArray Parameters: index - index to store a value in value - value to store at the specified index Throws: java.lang.ArrayIndexOutOfBoundsException - if index is less than zero. setExpansionFactor public void setExpansionFactor(float expansionFactor) Sets the expansionFactor. Throws IllegalArgumentException if the the following conditions are not met: expansionFactor > 1 contractionFactor >= expansionFactor Parameters: expansionFactor - the new expansion factor value. Throws: java.lang.IllegalArgumentException - if expansionFactor is <= 1 or greater than contractionFactor setExpansionMode public void setExpansionMode(int expansionMode) Sets the expansionMode. The specified value must be one of ADDITIVE_MODE, MULTIPLICATIVE_MODE. Parameters: expansionMode - The expansionMode to set. Throws: java.lang.IllegalArgumentException - if the specified mode value is not valid setInitialCapacity protected void setInitialCapacity(int initialCapacity) Sets the initial capacity. Should only be invoked by constructors. Parameters: initialCapacity - of the array Throws: java.lang.IllegalArgumentException - if initialCapacity is not positive. setNumElements public 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. This function will also expand the internal array as needed. Parameters: i - a new number of elements Throws: java.lang.IllegalArgumentException - if i is negative. start public int start() Returns the starting index of the internal array. The starting index is the position of the first addressable element in the internal storage array. The addressable elements in the array are internalArray[startIndex],...,internalArray[startIndex + numElements -1] Returns: starting index copy public static void copy(ResizableDoubleArray source, ResizableDoubleArray dest) Copies source to dest, copying the underlying data, so dest is a new, independent copy of source. Does not contract before the copy. Obtains synchronization locks on both source and dest (in that order) before performing the copy. Neither source nor dest may be null; otherwise a NullPointerException is thrown Parameters: source - ResizableDoubleArray to copy dest - ResizableArray to replace with a copy of the source array Since: 2.0 copy public ResizableDoubleArray 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 Since: 2.0 equals public boolean equals(java.lang.Object object) Returns true iff object is a ResizableDoubleArray with the same properties as this and an identical internal storage array. Overrides: equals in class java.lang.Object Parameters: object - object to be compared for equality with this Returns: true iff object is a ResizableDoubleArray with the same data and properties as this Since: 2.0 hashCode public int hashCode() Returns a hash code consistent with equals. Overrides: hashCode in class java.lang.Object Returns: hash code representing this ResizableDoubleArray Since: 2.0

Class ResizableDoubleArray

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

ADDITIVE_MODE

MULTIPLICATIVE_MODE

contractionCriteria

expansionFactor

expansionMode

initialCapacity

internalArray

numElements

startIndex

Constructor Detail

ResizableDoubleArray

ResizableDoubleArray

ResizableDoubleArray

ResizableDoubleArray

ResizableDoubleArray

ResizableDoubleArray

ResizableDoubleArray

Method Detail

addElement

addElements

addElementRolling

substituteMostRecentElement

checkContractExpand

clear

contract

discardFrontElements

discardMostRecentElements

expand

getContractionCriteria

getElement

getElements

getExpansionFactor

getExpansionMode

getNumElements

getValues

getInternalValues

setContractionCriteria

setElement

setExpansionFactor

setExpansionMode

setInitialCapacity

setNumElements

start

copy

copy

equals

hashCode