/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math.util;
import java.io.Serializable;
import java.util.Arrays;
import org.apache.commons.math.MathRuntimeException;
import org.apache.commons.math.exception.util.LocalizedFormats;
/**
* <p>
* A variable length {@link DoubleArray} implementation that automatically
* handles expanding and contracting its internal storage array as elements
* are added and removed.
* </p>
* <p>
* The internal storage array starts with capacity determined by the
* <code>initialCapacity</code> property, which can be set by the constructor.
* The default initial capacity is 16. Adding elements using
* {@link #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
* <code>expansionMode</code> and <code>expansionFactor</code> properties.
* The <code>expansionMode</code> determines whether the size of the array is
* multiplied by the <code>expansionFactor</code> (MULTIPLICATIVE_MODE) or if
* the expansion is additive (ADDITIVE_MODE -- <code>expansionFactor</code>
* storage locations added). The default <code>expansionMode</code> is
* MULTIPLICATIVE_MODE and the default <code>expansionFactor</code>
* is 2.0.
* </p>
* <p>
* The {@link #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 {@link #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 <code>numElements</code> property) and if the difference
* is too large, the internal array is contracted to size
* <code>numElements + 1.</code> The determination of when the internal
* storage array is "too large" depends on the <code>expansionMode</code> and
* <code>contractionFactor</code> properties. If the <code>expansionMode</code>
* is <code>MULTIPLICATIVE_MODE</code>, contraction is triggered when the
* ratio between storage array length and <code>numElements</code> exceeds
* <code>contractionFactor.</code> If the <code>expansionMode</code>
* is <code>ADDITIVE_MODE,</code> the number of excess storage locations
* is compared to <code>contractionFactor.</code>
* </p>
* <p>
* To avoid cycles of expansions and contractions, the
* <code>expansionFactor</code> must not exceed the
* <code>contractionFactor.</code> Constructors and mutators for both of these
* properties enforce this requirement, throwing IllegalArgumentException if it
* is violated.
* </p>
* @version $Id: ResizableDoubleArray.java 1131229 2011-06-03 20:49:25Z luc $
*/
public class ResizableDoubleArray implements DoubleArray, Serializable {
/** additive expansion mode */
public static final int ADDITIVE_MODE = 1;
/** multiplicative expansion mode */
public static final int MULTIPLICATIVE_MODE = 0;
/** Serializable version identifier */
private static final long serialVersionUID = -3485529955529426875L;
/**
* 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 contractionCriteria = 2.5f;
/**
* The expansion factor of the array. When the array needs to be expanded,
* the new array size will be
* <code>internalArray.length * expansionFactor</code>
* if <code>expansionMode</code> is set to MULTIPLICATIVE_MODE, or
* <code>internalArray.length + expansionFactor</code> if
* <code>expansionMode</code> is set to ADDITIVE_MODE.
*/
protected float expansionFactor = 2.0f;
/**
* Determines whether array expansion by <code>expansionFactor</code>
* is additive or multiplicative.
*/
protected int expansionMode = MULTIPLICATIVE_MODE;
/**
* The initial capacity of the array. Initial capacity is not exposed as a
* property as it is only meaningful when passed to a constructor.
*/
protected int initialCapacity = 16;
/**
* The internal storage array.
*/
protected double[] internalArray;
/**
* The number of addressable elements in the array. Note that this
* has nothing to do with the length of the internal storage array.
*/
protected int numElements = 0;
/**
* The position of the first addressable element in the internal storage
* array. The addressable elements in the array are <code>
* internalArray[startIndex],...,internalArray[startIndex + numElements -1]
* </code>
*/
protected int startIndex = 0;
/**
* Create a ResizableArray with default properties.
* <ul>
* <li><code>initialCapacity = 16</code></li>
* <li><code>expansionMode = MULTIPLICATIVE_MODE</code></li>
* <li><code>expansionFactor = 2.5</code></li>
* <li><code>contractionFactor = 2.0</code></li>
* </ul>
*/
public ResizableDoubleArray() {
internalArray = new double[initialCapacity];
}
/**
* Create a ResizableArray with the specified initial capacity. Other
* properties take default values:
* <ul>
* <li><code>expansionMode = MULTIPLICATIVE_MODE</code></li>
* <li><code>expansionFactor = 2.5</code></li>
* <li><code>contractionFactor = 2.0</code></li>
* </ul>
* @param initialCapacity The initial size of the internal storage array
* @throws IllegalArgumentException if initialCapacity is not > 0
*/
public ResizableDoubleArray(int initialCapacity) {
setInitialCapacity(initialCapacity);
internalArray = new double[this.initialCapacity];
}
/**
* 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:
* <ul>
* <li><code>initialCapacity = 16</code></li>
* <li><code>expansionMode = MULTIPLICATIVE_MODE</code></li>
* <li><code>expansionFactor = 2.5</code></li>
* <li><code>contractionFactor = 2.0</code></li>
* </ul>
*
* @param initialArray initial array
* @since 2.2
*/
public ResizableDoubleArray(double[] initialArray) {
if (initialArray == null) {
this.internalArray = new double[initialCapacity];
} else {
this.internalArray = new double[initialArray.length];
System.arraycopy(initialArray, 0, this.internalArray, 0, initialArray.length);
initialCapacity = initialArray.length;
numElements = initialArray.length;
}
}
/**
* <p>
* Create a ResizableArray with the specified initial capacity
* and expansion factor. The remaining properties take default
* values:
* <ul>
* <li><code>expansionMode = MULTIPLICATIVE_MODE</code></li>
* <li><code>contractionFactor = 0.5 + expansionFactor</code></li>
* </ul></p>
* <p>
* Throws IllegalArgumentException if the following conditions are
* not met:
* <ul>
* <li><code>initialCapacity > 0</code></li>
* <li><code>expansionFactor > 1</code></li>
* </ul></p>
*
* @param initialCapacity The initial size of the internal storage array
* @param expansionFactor the array will be expanded based on this
* parameter
* @throws IllegalArgumentException if parameters are not valid
*/
public ResizableDoubleArray(int initialCapacity, float expansionFactor) {
this.expansionFactor = expansionFactor;
setInitialCapacity(initialCapacity);
internalArray = new double[initialCapacity];
setContractionCriteria(expansionFactor +0.5f);
}
/**
* <p>
* Create a ResizableArray with the specified initialCapacity,
* expansionFactor, and contractionCriteria. The <code>expansionMode</code>
* will default to <code>MULTIPLICATIVE_MODE.</code></p>
* <p>
* Throws IllegalArgumentException if the following conditions are
* not met:
* <ul>
* <li><code>initialCapacity > 0</code></li>
* <li><code>expansionFactor > 1</code></li>
* <li><code>contractionFactor >= expansionFactor</code></li>
* </ul></p>
* @param initialCapacity The initial size of the internal storage array
* @param expansionFactor the array will be expanded based on this
* parameter
* @param contractionCriteria The contraction Criteria.
* @throws IllegalArgumentException if parameters are not valid
*/
public ResizableDoubleArray(int initialCapacity, float expansionFactor,
float contractionCriteria) {
this.expansionFactor = expansionFactor;
setContractionCriteria(contractionCriteria);
setInitialCapacity(initialCapacity);
internalArray = new double[initialCapacity];
}
/**
* <p>
* Create a ResizableArray with the specified properties.</p>
* <p>
* Throws IllegalArgumentException if the following conditions are
* not met:
* <ul>
* <li><code>initialCapacity > 0</code></li>
* <li><code>expansionFactor > 1</code></li>
* <li><code>contractionFactor >= expansionFactor</code></li>
* <li><code>expansionMode in {MULTIPLICATIVE_MODE, ADDITIVE_MODE}</code>
* </li>
* </ul></p>
*
* @param initialCapacity the initial size of the internal storage array
* @param expansionFactor the array will be expanded based on this
* parameter
* @param contractionCriteria the contraction Criteria
* @param expansionMode the expansion mode
* @throws IllegalArgumentException if parameters are not valid
*/
public ResizableDoubleArray(int initialCapacity, float expansionFactor,
float contractionCriteria, int expansionMode) {
this.expansionFactor = expansionFactor;
setContractionCriteria(contractionCriteria);
setInitialCapacity(initialCapacity);
setExpansionMode(expansionMode);
internalArray = new double[initialCapacity];
}
/**
* 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.
*
* @param original array to copy
* @since 2.0
*/
public ResizableDoubleArray(ResizableDoubleArray original) {
copy(original, this);
}
/**
* Adds an element to the end of this expandable array.
*
* @param value to be added to end of array
*/
public synchronized void addElement(double value) {
numElements++;
if ((startIndex + numElements) > internalArray.length) {
expand();
}
internalArray[startIndex + (numElements - 1)] = value;
if (shouldContract()) {
contract();
}
}
/**
* Adds several element to the end of this expandable array.
*
* @param values to be added to end of array
* @since 2.2
*/
public synchronized void addElements(double[] values) {
final double[] tempArray = new double[numElements + values.length + 1];
System.arraycopy(internalArray, startIndex, tempArray, 0, numElements);
System.arraycopy(values, 0, tempArray, numElements, values.length);
internalArray = tempArray;
startIndex = 0;
numElements += values.length;
}
/**
* <p>
* 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.
* </p>
* <p>
* 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.
* </p>
*
* @param value the value to be added to the array
* @return the value which has been discarded or "pushed" out of the array
* by this rolling insert
*/
public synchronized double addElementRolling(double value) {
double discarded = internalArray[startIndex];
if ((startIndex + (numElements + 1)) > internalArray.length) {
expand();
}
// Increment the start index
startIndex += 1;
// Add the new value
internalArray[startIndex + (numElements - 1)] = value;
// Check the contraction criteria
if (shouldContract()) {
contract();
}
return discarded;
}
/**
* Substitutes <code>value</code> for the most recently added value.
* Returns the value that has been replaced. If the array is empty (i.e.
* if {@link #numElements} is zero), a MathRuntimeException is thrown.
*
* @param value new value to substitute for the most recently added value
* @return value that has been replaced in the array
* @since 2.0
*/
public synchronized double substituteMostRecentElement(double value) {
if (numElements < 1) {
throw MathRuntimeException.createArrayIndexOutOfBoundsException(
LocalizedFormats.CANNOT_SUBSTITUTE_ELEMENT_FROM_EMPTY_ARRAY);
}
double discarded = internalArray[startIndex + (numElements - 1)];
internalArray[startIndex + (numElements - 1)] = value;
return discarded;
}
/**
* Checks the expansion factor and the contraction criteria and throws an
* IllegalArgumentException if the contractionCriteria is less than the
* expansionCriteria
*
* @param expansion factor to be checked
* @param contraction criteria to be checked
* @throws IllegalArgumentException if the contractionCriteria is less than
* the expansionCriteria.
*/
protected void checkContractExpand(float contraction, float expansion) {
if (contraction < expansion) {
throw MathRuntimeException.createIllegalArgumentException(
LocalizedFormats.CONTRACTION_CRITERIA_SMALLER_THAN_EXPANSION_FACTOR,
contraction, expansion);
}
if (contraction <= 1.0) {
throw MathRuntimeException.createIllegalArgumentException(
LocalizedFormats.CONTRACTION_CRITERIA_SMALLER_THAN_ONE,
contraction);
}
if (expansion <= 1.0) {
throw MathRuntimeException.createIllegalArgumentException(
LocalizedFormats.EXPANSION_FACTOR_SMALLER_THAN_ONE,
expansion);
}
}
/**
* Clear the array, reset the size to the initialCapacity and the number
* of elements to zero.
*/
public synchronized void clear() {
numElements = 0;
startIndex = 0;
internalArray = new double[initialCapacity];
}
/**
* 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.
*/
public synchronized void contract() {
double[] tempArray = new double[numElements + 1];
// Copy and swap - copy only the element array from the src array.
System.arraycopy(internalArray, startIndex, tempArray, 0, numElements);
internalArray = tempArray;
// Reset the start index to zero
startIndex = 0;
}
/**
* Discards the <code>i<code> initial elements of the array. For example,
* if the array contains the elements 1,2,3,4, invoking
* <code>discardFrontElements(2)</code> will cause the first two elements
* to be discarded, leaving 3,4 in the array. Throws illegalArgumentException
* if i exceeds numElements.
*
* @param i the number of elements to discard from the front of the array
* @throws IllegalArgumentException if i is greater than numElements.
* @since 2.0
*/
public synchronized void discardFrontElements(int i) {
discardExtremeElements(i,true);
}
/**
* Discards the <code>i<code> last elements of the array. For example,
* if the array contains the elements 1,2,3,4, invoking
* <code>discardMostRecentElements(2)</code> will cause the last two elements
* to be discarded, leaving 1,2 in the array. Throws illegalArgumentException
* if i exceeds numElements.
*
* @param i the number of elements to discard from the end of the array
* @throws IllegalArgumentException if i is greater than numElements.
* @since 2.0
*/
public synchronized void discardMostRecentElements(int i) {
discardExtremeElements(i,false);
}
/**
* Discards the <code>i<code> first or last elements of the array,
* depending on the value of <code>front</code>.
* For example, if the array contains the elements 1,2,3,4, invoking
* <code>discardExtremeElements(2,false)</code> will cause the last two elements
* to be discarded, leaving 1,2 in the array.
* For example, if the array contains the elements 1,2,3,4, invoking
* <code>discardExtremeElements(2,true)</code> will cause the first two elements
* to be discarded, leaving 3,4 in the array.
* Throws illegalArgumentException
* if i exceeds numElements.
*
* @param i the number of elements to discard from the front/end of the array
* @param front true if elements are to be discarded from the front
* of the array, false if elements are to be discarded from the end
* of the array
* @throws IllegalArgumentException if i is greater than numElements.
* @since 2.0
*/
private synchronized void discardExtremeElements(int i,boolean front) {
if (i > numElements) {
throw MathRuntimeException.createIllegalArgumentException(
LocalizedFormats.TOO_MANY_ELEMENTS_TO_DISCARD_FROM_ARRAY,
i, numElements);
} else if (i < 0) {
throw MathRuntimeException.createIllegalArgumentException(
LocalizedFormats.CANNOT_DISCARD_NEGATIVE_NUMBER_OF_ELEMENTS,
i);
} else {
// "Subtract" this number of discarded from numElements
numElements -= i;
if (front) startIndex += i;
}
if (shouldContract()) {
contract();
}
}
/**
* Expands the internal storage array using the expansion factor.
* <p>
* if <code>expansionMode</code> is set to MULTIPLICATIVE_MODE,
* the new array size will be <code>internalArray.length * expansionFactor.</code>
* If <code>expansionMode</code> is set to ADDITIVE_MODE, the length
* after expansion will be <code>internalArray.length + expansionFactor</code>
* </p>
*/
protected synchronized void expand() {
// notice the use of FastMath.ceil(), this guarantees that we will always
// have an array of at least currentSize + 1. Assume that the
// current initial capacity is 1 and the expansion factor
// is 1.000000000000000001. The newly calculated size will be
// rounded up to 2 after the multiplication is performed.
int newSize = 0;
if (expansionMode == MULTIPLICATIVE_MODE) {
newSize = (int) FastMath.ceil(internalArray.length * expansionFactor);
} else {
newSize = internalArray.length + FastMath.round(expansionFactor);
}
double[] tempArray = new double[newSize];
// Copy and swap
System.arraycopy(internalArray, 0, tempArray, 0, internalArray.length);
internalArray = tempArray;
}
/**
* Expands the internal storage array to the specified size.
*
* @param size Size of the new internal storage array
*/
private synchronized void expandTo(int size) {
double[] tempArray = new double[size];
// Copy and swap
System.arraycopy(internalArray, 0, tempArray, 0, internalArray.length);
internalArray = tempArray;
}
/**
* The contraction criteria defines when the internal array will contract
* to store only the number of elements in the element array.
* If the <code>expansionMode</code> is <code>MULTIPLICATIVE_MODE</code>,
* contraction is triggered when the ratio between storage array length
* and <code>numElements</code> exceeds <code>contractionFactor</code>.
* If the <code>expansionMode</code> is <code>ADDITIVE_MODE</code>, the
* number of excess storage locations is compared to
* <code>contractionFactor.</code>
*
* @return the contraction criteria used to reclaim memory.
*/
public float getContractionCriteria() {
return contractionCriteria;
}
/**
* Returns the element at the specified index
*
* @param index index to fetch a value from
* @return value stored at the specified index
* @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
* zero or is greater than <code>getNumElements() - 1</code>.
*/
public synchronized double getElement(int index) {
if (index >= numElements) {
throw MathRuntimeException.createArrayIndexOutOfBoundsException(
LocalizedFormats.INDEX_LARGER_THAN_MAX,
index, numElements - 1);
} else if (index >= 0) {
return internalArray[startIndex + index];
} else {
throw MathRuntimeException.createArrayIndexOutOfBoundsException(
LocalizedFormats.CANNOT_RETRIEVE_AT_NEGATIVE_INDEX,
index);
}
}
/**
* Returns a double array containing the elements of this
* <code>ResizableArray</code>. 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 <code>ResizableArray.</code>
* @return the double array.
*/
public synchronized double[] getElements() {
double[] elementArray = new double[numElements];
System.arraycopy( internalArray, startIndex, elementArray, 0,
numElements);
return elementArray;
}
/**
* The expansion factor controls the size of a new array when an array
* needs to be expanded. The <code>expansionMode</code>
* determines whether the size of the array is multiplied by the
* <code>expansionFactor</code> (MULTIPLICATIVE_MODE) or if
* the expansion is additive (ADDITIVE_MODE -- <code>expansionFactor</code>
* storage locations added). The default <code>expansionMode</code> is
* MULTIPLICATIVE_MODE and the default <code>expansionFactor</code>
* is 2.0.
*
* @return the expansion factor of this expandable double array
*/
public float getExpansionFactor() {
return expansionFactor;
}
/**
* The <code>expansionMode</code> determines whether the internal storage
* array grows additively (ADDITIVE_MODE) or multiplicatively
* (MULTIPLICATIVE_MODE) when it is expanded.
*
* @return Returns the expansionMode.
*/
public int getExpansionMode() {
return expansionMode;
}
/**
* Notice the package scope on this method. This method is simply here
* for the JUnit test, it allows us check if the expansion is working
* properly after a number of expansions. This is not meant to be a part
* of the public interface of this class.
*
* @return the length of the internal storage array.
*/
synchronized int getInternalLength() {
return internalArray.length;
}
/**
* Returns the number of elements currently in the array. Please note
* that this is different from the length of the internal storage array.
*
* @return number of elements
*/
public synchronized int getNumElements() {
return numElements;
}
/**
* 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 <code>startIndex</code> is
* required (available via the {@link #start} method). This method should
* only be used in cases where copying the internal array is not practical.
* The {@link #getElements} method should be used in all other cases.
*
*
* @return the internal storage array used by this object
* @since 2.0
*/
public synchronized double[] getInternalValues() {
return internalArray;
}
/**
* Sets the contraction criteria for this ExpandContractDoubleArray.
*
* @param contractionCriteria contraction criteria
*/
public void setContractionCriteria(float contractionCriteria) {
checkContractExpand(contractionCriteria, getExpansionFactor());
synchronized(this) {
this.contractionCriteria = contractionCriteria;
}
}
/**
* Sets the element at the specified index. If the specified index is greater than
* <code>getNumElements() - 1</code>, the <code>numElements</code> property
* is increased to <code>index +1</code> 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).
*
* @param index index to store a value in
* @param value value to store at the specified index
* @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
* zero.
*/
public synchronized void setElement(int index, double value) {
if (index < 0) {
throw MathRuntimeException.createArrayIndexOutOfBoundsException(
LocalizedFormats.CANNOT_SET_AT_NEGATIVE_INDEX,
index);
}
if (index + 1 > numElements) {
numElements = index + 1;
}
if ((startIndex + index) >= internalArray.length) {
expandTo(startIndex + (index + 1));
}
internalArray[startIndex + index] = value;
}
/**
* Sets the expansionFactor. Throws IllegalArgumentException if the
* the following conditions are not met:
* <ul>
* <li><code>expansionFactor > 1</code></li>
* <li><code>contractionFactor >= expansionFactor</code></li>
* </ul>
* @param expansionFactor the new expansion factor value.
* @throws IllegalArgumentException if expansionFactor is <= 1 or greater
* than contractionFactor
*/
public void setExpansionFactor(float expansionFactor) {
checkContractExpand(getContractionCriteria(), expansionFactor);
// The check above verifies that the expansion factor is > 1.0;
synchronized(this) {
this.expansionFactor = expansionFactor;
}
}
/**
* Sets the <code>expansionMode</code>. The specified value must be one of
* ADDITIVE_MODE, MULTIPLICATIVE_MODE.
*
* @param expansionMode The expansionMode to set.
* @throws IllegalArgumentException if the specified mode value is not valid
*/
public void setExpansionMode(int expansionMode) {
if (expansionMode != MULTIPLICATIVE_MODE &&
expansionMode != ADDITIVE_MODE) {
throw MathRuntimeException.createIllegalArgumentException(
LocalizedFormats.UNSUPPORTED_EXPANSION_MODE,
expansionMode, MULTIPLICATIVE_MODE, "MULTIPLICATIVE_MODE",
ADDITIVE_MODE, "ADDITIVE_MODE");
}
synchronized(this) {
this.expansionMode = expansionMode;
}
}
/**
* Sets the initial capacity. Should only be invoked by constructors.
*
* @param initialCapacity of the array
* @throws IllegalArgumentException if <code>initialCapacity</code> is not
* positive.
*/
protected void setInitialCapacity(int initialCapacity) {
if (initialCapacity > 0) {
synchronized(this) {
this.initialCapacity = initialCapacity;
}
} else {
throw MathRuntimeException.createIllegalArgumentException(
LocalizedFormats.INITIAL_CAPACITY_NOT_POSITIVE,
initialCapacity);
}
}
/**
* 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.
*
* @param i a new number of elements
* @throws IllegalArgumentException if <code>i</code> is negative.
*/
public synchronized void setNumElements(int i) {
// If index is negative thrown an error
if (i < 0) {
throw MathRuntimeException.createIllegalArgumentException(
LocalizedFormats.INDEX_NOT_POSITIVE,
i);
}
// Test the new num elements, check to see if the array needs to be
// expanded to accommodate this new number of elements
if ((startIndex + i) > internalArray.length) {
expandTo(startIndex + i);
}
// Set the new number of elements to new value
numElements = i;
}
/**
* Returns true if the internal storage array has too many unused
* storage positions.
*
* @return true if array satisfies the contraction criteria
*/
private synchronized boolean shouldContract() {
if (expansionMode == MULTIPLICATIVE_MODE) {
return (internalArray.length / ((float) numElements)) > contractionCriteria;
} else {
return (internalArray.length - numElements) > contractionCriteria;
}
}
/**
* 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 <code>
* internalArray[startIndex],...,internalArray[startIndex + numElements -1]
* </code>
*
* @return starting index
*/
public synchronized int start() {
return startIndex;
}
/**
* <p>Copies source to dest, copying the underlying data, so dest is
* a new, independent copy of source. Does not contract before
* the copy.</p>
*
* <p>Obtains synchronization locks on both source and dest
* (in that order) before performing the copy.</p>
*
* <p>Neither source nor dest may be null; otherwise a NullPointerException
* is thrown</p>
*
* @param source ResizableDoubleArray to copy
* @param dest ResizableArray to replace with a copy of the source array
* @since 2.0
*
*/
public static void copy(ResizableDoubleArray source, ResizableDoubleArray dest) {
synchronized(source) {
synchronized(dest) {
dest.initialCapacity = source.initialCapacity;
dest.contractionCriteria = source.contractionCriteria;
dest.expansionFactor = source.expansionFactor;
dest.expansionMode = source.expansionMode;
dest.internalArray = new double[source.internalArray.length];
System.arraycopy(source.internalArray, 0, dest.internalArray,
0, dest.internalArray.length);
dest.numElements = source.numElements;
dest.startIndex = source.startIndex;
}
}
}
/**
* Returns a copy of the ResizableDoubleArray. Does not contract before
* the copy, so the returned object is an exact copy of this.
*
* @return a new ResizableDoubleArray with the same data and configuration
* properties as this
* @since 2.0
*/
public synchronized ResizableDoubleArray copy() {
ResizableDoubleArray result = new ResizableDoubleArray();
copy(this, result);
return result;
}
/**
* Returns true iff object is a ResizableDoubleArray with the same properties
* as this and an identical internal storage array.
*
* @param object object to be compared for equality with this
* @return true iff object is a ResizableDoubleArray with the same data and
* properties as this
* @since 2.0
*/
@Override
public boolean equals(Object object) {
if (object == this ) {
return true;
}
if (object instanceof ResizableDoubleArray == false) {
return false;
}
synchronized(this) {
synchronized(object) {
boolean result = true;
ResizableDoubleArray other = (ResizableDoubleArray) object;
result = result && (other.initialCapacity == initialCapacity);
result = result && (other.contractionCriteria == contractionCriteria);
result = result && (other.expansionFactor == expansionFactor);
result = result && (other.expansionMode == expansionMode);
result = result && (other.numElements == numElements);
result = result && (other.startIndex == startIndex);
if (!result) {
return false;
} else {
return Arrays.equals(internalArray, other.internalArray);
}
}
}
}
/**
* Returns a hash code consistent with equals.
*
* @return hash code representing this ResizableDoubleArray
* @since 2.0
*/
@Override
public synchronized int hashCode() {
int[] hashData = new int[7];
hashData[0] = new Float(expansionFactor).hashCode();
hashData[1] = new Float(contractionCriteria).hashCode();
hashData[2] = expansionMode;
hashData[3] = Arrays.hashCode(internalArray);
hashData[4] = initialCapacity;
hashData[5] = numElements;
hashData[6] = startIndex;
return Arrays.hashCode(hashData);
}
}