de.lmu.ifi.dbs.elki.utilities
Class Util

java.lang.Object
  de.lmu.ifi.dbs.elki.utilities.Util

public final class Util
extends Object

This class collects various static helper methods. For helper methods related to special application fields see other utilities classes.

See Also:

de.lmu.ifi.dbs.elki.utilities

Nested Class Summary

static class

Util.MaskedArrayList<T> This class is a virtual collection based on masking an array list using a bit mask.

Constructor Summary

Util()

Method Summary

static <O> void	addToList(List<O> list, O[] array) Adds the entries of the specified array to the end of the given list.
static int	arrayFind(String[] arr, Object ref) Search an (unsorted) array linearly for an object.
static List<Integer>	convertBitSetToListInt(BitSet b, int off) Convert a bit set to a list of integers, representing bits that are set
static double[]	convertToDoubles(float[] values) Converts the specified array of doubles to an array of floats.
static double[]	convertToDoubles(List<Double> values) Converts the specified list of Double objects to an array of doubles.
static float[]	convertToFloat(double[] values) Converts the specified array of doubles to an array of floats.
static List<Float>	convertToFloat(List<Double> values) Converts the specified list of double objects to a list of float objects.
static double[]	copy(double[] array) Returns a new double array containing the same objects as are contained in the given array.
static String[]	copy(String[] array) Returns a new String array containing the same objects as are contained in the given array.
static String	getFilePrefix(String fileName) Returns the prefix of the specified fileName (i.e. the name of the file without extension).
static int	getIndexOfMaximum(double[] values) Returns the index of the maximum of the given values.
static int	indexOfNthSetBit(BitSet bitset, int nthSetBit) Returns the index of the nth set bit in the given BitSet.
static BitSet	int2Bit(int n) Converts the specified positive integer value into a bit representation, where bit 0 denotes 20, bit 1 denotes 21 etc.
static <O> void	intersection(Set<O> s1, Set<O> s2, Set<O> result) Provides the intersection of the two specified sets in the given result set.
static String[]	joinArray(String[] array1, String[] array2) Joins the specified arrays.
static int	mixHashCodes(int... hash) Mix multiple hashcodes into one.
static BitSet	parseBitSet(char[] s) Returns a new BitSet initialized to the values represented by the specified char array only containing '0' and '1' values.
static BitSet	parseBitSet(String s) Returns a new BitSet initialized to the values represented by the specified String only containing 0 and 1 values.
static double[]	parseDoubles(String s) Returns a new Double array initialized to the values represented by the specified String and separated by comma, as performed by the valueOf method of class Double.
static float[]	parseFloats(String s) Returns a new Float array initialized to the values represented by the specified String and separated by comma, as performed by the valueOf method of class Float.
static String	parseSelectedBits(BitSet b, String sep) Returns a string that represents the selected bits of the specified BitSet, while the first bit starts with 1.
static <O> void	print(List<O> list, String separator, PrintStream out) Prints the given list to the specified PrintStream.
static DoubleVector	project(DoubleVector v, BitSet selectedAttributes) Provides a new DoubleVector as a projection on the specified attributes.
static SparseFloatVector	project(SparseFloatVector v, BitSet selectedAttributes) Provides a new SparseFloatVector as a projection on the specified attributes.
static BitSet	randomBitSet(int cardinality, int capacity, Random random) Creates a new BitSet of fixed cardinality with randomly set bits.
static double[]	unbox(Double[] array) Returns the unboxed double array of the given Object Double array.
static double[]	unbox(Number[] array) Returns the unboxed double array of the given Object Number array.
static float[]	unboxToFloat(Number[] array) Returns the unboxed float array of the given Object Number array.

Methods inherited from class java.lang.Object

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

Constructor Detail

Util

public Util()

Method Detail

getFilePrefix

public static String getFilePrefix(String fileName)

Returns the prefix of the specified fileName (i.e. the name of the file without extension).

Parameters:

fileName - the name of the file

Returns:

the prefix of the specified fileName

copy

public static String[] copy(String[] array)

Returns a new String array containing the same objects as are contained in the given array.

Parameters:

array - an array to copy

Returns:

the copied array

copy

public static double[] copy(double[] array)

Returns a new double array containing the same objects as are contained in the given array.

Parameters:

array - an array to copy

Returns:

the copied array

unbox

public static double[] unbox(Double[] array)

Returns the unboxed double array of the given Object Double array.

Parameters:

array - the array to be unboxed

Returns:

the unboxed double array

unbox

public static double[] unbox(Number[] array)

Returns the unboxed double array of the given Object Number array.

Parameters:

array - the array to be unboxed

Returns:

the unboxed double array

unboxToFloat

public static float[] unboxToFloat(Number[] array)

Returns the unboxed float array of the given Object Number array.

Parameters:

array - the array to be unboxed

Returns:

the unboxed float array

parseDoubles

public static double[] parseDoubles(String s)

Returns a new Double array initialized to the values represented by the specified String and separated by comma, as performed by the valueOf method of class Double.

Parameters:

s - the string to be parsed.

Returns:

a new Double array represented by s

parseFloats

public static float[] parseFloats(String s)

Returns a new Float array initialized to the values represented by the specified String and separated by comma, as performed by the valueOf method of class Float.

Parameters:

s - the string to be parsed.

Returns:

a new Float array represented by s

convertToFloat

public static List<Float> convertToFloat(List<Double> values)

Converts the specified list of double objects to a list of float objects.

Parameters:

values - the list of double objects to be converted

Returns:

the converted list of float objects

convertToFloat

public static float[] convertToFloat(double[] values)

Converts the specified array of doubles to an array of floats.

Parameters:

values - the array of doubles to be converted

Returns:

the converted array of floats

convertToDoubles

public static double[] convertToDoubles(float[] values)

Converts the specified array of doubles to an array of floats.

Parameters:

values - the array of doubles to be converted

Returns:

the converted array of floats

convertToDoubles

public static double[] convertToDoubles(List<Double> values)

Converts the specified list of Double objects to an array of doubles.

Parameters:

values - the list of Double objects to be converted

Returns:

the converted array of doubles

print

public static <O> void print(List<O> list,
                             String separator,
                             PrintStream out)

Prints the given list to the specified PrintStream. The list entries are separated by the specified separator. The last entry is not followed by a separator. Thus, if a newline is used as separator, it might make sense to print a newline to the PrintStream after calling this method.

Type Parameters:

O - object class

Parameters:

list - the list to be printed

separator - the separator to separate entries of the list

out - the target PrintStream

getIndexOfMaximum

public static int getIndexOfMaximum(double[] values)
                             throws ArrayIndexOutOfBoundsException

Returns the index of the maximum of the given values. If no value is bigger than the first, the index of the first entry is returned.

Parameters:

values - the values to find the index of the maximum

Returns:

the index of the maximum in the given values

Throws:

ArrayIndexOutOfBoundsException - if values.length==0

parseBitSet

public static BitSet parseBitSet(String s)

Returns a new BitSet initialized to the values represented by the specified String only containing 0 and 1 values.

Parameters:

s - the string to be parsed.

Returns:

a new BitSet represented by s

parseBitSet

public static BitSet parseBitSet(char[] s)

Returns a new BitSet initialized to the values represented by the specified char array only containing '0' and '1' values.

Parameters:

s - the char array to be parsed.

Returns:

a new BitSet represented by s

parseSelectedBits

public static String parseSelectedBits(BitSet b,
                                       String sep)

Returns a string that represents the selected bits of the specified BitSet, while the first bit starts with 1. The selected bits are separated by the specified separator sep. If sep is ",", the result is suitable as a parameter for an IntListParameter.

Parameters:

b - the bit set to be parsed

sep - the separator

Returns:

a string representing the selected bits of the specified BitSet

convertBitSetToListInt

public static List<Integer> convertBitSetToListInt(BitSet b,
                                                   int off)

Convert a bit set to a list of integers, representing bits that are set

Parameters:

b - Bitset

off - Offset, set to 0 to start counting at 0, 1 to start counting at 1.

Returns:

List

randomBitSet

public static BitSet randomBitSet(int cardinality,
                                  int capacity,
                                  Random random)

Creates a new BitSet of fixed cardinality with randomly set bits.

Parameters:

cardinality - the cardinality of the BitSet to create

capacity - the capacity of the BitSet to create - the randomly generated indices of the bits set to true will be uniformly distributed between 0 (inclusive) and capacity (exclusive)

random - a Random Object to create the sequence of indices set to true - the same number occurring twice or more is ignored but the already selected bit remains true

Returns:

a new BitSet with randomly set bits

project

public static DoubleVector project(DoubleVector v,
                                   BitSet selectedAttributes)

Provides a new DoubleVector as a projection on the specified attributes. If the given DoubleVector has already an ID not null, the same ID is set in the returned new DoubleVector. Nevertheless, the returned DoubleVector is not backed by the given DoubleVector, i.e., any changes affecting v after calling this method will not affect the newly returned DoubleVector.

Parameters:

v - a DoubleVector to project

selectedAttributes - the attributes selected for projection

Returns:

a new DoubleVector as a projection on the specified attributes

Throws:

IllegalArgumentException - if the given selected attributes specify an attribute as selected which is out of range for the given DoubleVector.

See Also:

DoubleVector.doubleValue(int)

project

public static SparseFloatVector project(SparseFloatVector v,
                                        BitSet selectedAttributes)

Provides a new SparseFloatVector as a projection on the specified attributes. If the given SparseFloatVector has already an ID not null, the same ID is set in the returned new SparseFloatVector. Nevertheless, the returned SparseFloatVector is not backed by the given SparseFloatVector, i.e., any changes affecting v after calling this method will not affect the newly returned SparseFloatVector.

Parameters:

v - a SparseFloatVector to project

selectedAttributes - the attributes selected for projection

Returns:

a new SparseFloatVector as a projection on the specified attributes

Throws:

IllegalArgumentException - if the given selected attributes specify an attribute as selected which is out of range for the given SparseFloatVector.

indexOfNthSetBit

public static int indexOfNthSetBit(BitSet bitset,
                                   int nthSetBit)
                            throws IllegalArgumentException

Returns the index of the n^th set bit in the given BitSet. For the parameter nthSetBit, following condition is assumed: 1 ≤ nthSetBit ≤ bitset.cardinality(). Otherwise, i.e., if the Bitset contains less than nthSetBit set bits or nthSetBit is not a positive number, the method throws an IllegalArgumentException. The worstcase runtime complexity of this method is in O( bitset.cardinality()).

Parameters:

bitset - the BitSet to derive the index of the n^th set bit in

nthSetBit - which set bit to derive the index of

Returns:

the index of the n^th set bit in the given BitSet

Throws:

IllegalArgumentException - if the Bitset contains less than nthSetBit set bits or nthSetBit is not a positive number

intersection

public static <O> void intersection(Set<O> s1,
                                    Set<O> s2,
                                    Set<O> result)

Provides the intersection of the two specified sets in the given result set.

Type Parameters:

O - object class

Parameters:

s1 - the first set

s2 - the second set

result - the result set

int2Bit

public static BitSet int2Bit(int n)

Converts the specified positive integer value into a bit representation, where bit 0 denotes 2⁰, bit 1 denotes 2¹ etc.

Parameters:

n - the positive integer value to be converted

Returns:

the specified integer value into a bit representation

joinArray

public static String[] joinArray(String[] array1,
                                 String[] array2)

Joins the specified arrays.

Parameters:

array1 - the first array

array2 - the second array

Returns:

a new array containing the entries of array1 and the array2.

addToList

public static <O> void addToList(List<O> list,
                                 O[] array)

Adds the entries of the specified array to the end of the given list.

Type Parameters:

O - object class

Parameters:

list - the list

array - the array containing the objects to be added to the list

arrayFind

public static int arrayFind(String[] arr,
                            Object ref)

Search an (unsorted) array linearly for an object.

Parameters:

arr - Array to search

ref - Object to search for

Returns:

Index of object or -1 if not found.

mixHashCodes

public static final int mixHashCodes(int... hash)

Mix multiple hashcodes into one.

Parameters:

hash - Hashcodes to mix

Returns:

Mixed hash code