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

Nested Classes

Modifier and Type	Class and Description
private static class	Util.ForwardComparator Regular comparator.

Field Summary

Fields

Modifier and Type	Field and Description
private static Comparator<?>	FORWARD Static instance

Constructor Summary

Constructors

Constructor and Description
Util()

Method Summary

Methods

Modifier and Type	Method and Description
static double[]	copy(double[] array) Returns a new double array containing the same objects as are contained in the given array.
static <T> Comparator<T>	forwardOrder() Compare two objects, forward.
static int	mixHashCodes(int... hash) Mix multiple hashcodes into one.
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 <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 <V extends SparseNumberVector<V,?>> V	project(V 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.

Methods inherited from class java.lang.Object

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

Field Detail

FORWARD

private static final Comparator<?> FORWARD

Static instance

Constructor Detail

Util

public Util()

Method Detail

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

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

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

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 <V extends SparseNumberVector<V,?>> V project(V 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.

mixHashCodes

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

Mix multiple hashcodes into one.

Parameters:

hash - Hashcodes to mix

Returns:

Mixed hash code

forwardOrder

public static final <T> Comparator<T> forwardOrder()

Compare two objects, forward. See Collections.reverseOrder() for a reverse comparator.

Returns:

Forward comparator