net.automatalib.commons.util.comparison

Class CmpUtil

java.lang.Object

net.automatalib.commons.util.comparison.CmpUtil

public final class CmpUtil
extends Object

Various methods for dealing with the comparison of objects.

Author:

Malte Isberner

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CmpUtil.NullOrdering Enum for controlling which rank is assigned to a null element when using a safe comparator (safeComparator(Comparator, NullOrdering)).

Method Summary

Modifier and Type	Method and Description
static <T extends List<U>,U extends Comparable<U>> Comparator<T>	canonicalComparator() Retrieves a canonical comparator for the given type, which has to be a List of Comparable types.
static <T extends List<? extends U>,U> Comparator<T>	canonicalComparator(Comparator<? super U> elemComp) Retrieves a canonical comparator for the given list type.
static int	canonicalCompare(int[] a1, int[] a2)
static <U extends Comparable<? super U>> int	canonicalCompare(List<? extends U> o1, List<? extends U> o2) Compares two Lists of Comparable elements with respect to canonical ordering.
static <U> int	canonicalCompare(List<? extends U> o1, List<? extends U> o2, Comparator<? super U> elemComparator) Compares two Lists with respect to canonical ordering.
static <U extends Comparable<U>,T extends Iterable<U>> Comparator<T>	lexComparator() Retrieves a lexicographical comparator for the given type, which has to be an Iterable of Comparable types.
static <T extends Iterable<U>,U> Comparator<T>	lexComparator(Comparator<U> elemComp) Retrieves a lexicographical comparator for the given type.
static int	lexCompare(int[] a1, int[] a2)
static <U extends Comparable<? super U>> int	lexCompare(Iterable<? extends U> o1, Iterable<? extends U> o2) Lexicographically compares two Iterables, whose element types are comparable.
static <U> int	lexCompare(Iterable<? extends U> o1, Iterable<? extends U> o2, Comparator<U> elemComparator) Lexicographically compares two Iterables.
static <T> Comparator<T>	safeComparator(Comparator<? super T> baseComp, CmpUtil.NullOrdering nullOrd) Retrieves a safe comparator, which can handle null element values.

Methods inherited from class java.lang.Object

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

Method Detail

canonicalCompare

public static <U> int canonicalCompare(List<? extends U> o1,
                                       List<? extends U> o2,
                                       Comparator<? super U> elemComparator)

Compares two Lists with respect to canonical ordering.

In canonical ordering, a sequence o1 is less than a sequence o2 if o1 is shorter than o2, or if they have the same length and o1 is lexicographically smaller than o2.

Parameters:

o1 - the first list

o2 - the second list

elemComparator - the comparator for comparing the single elements

Returns:

the result of the comparison

canonicalCompare

public static int canonicalCompare(int[] a1,
                                   int[] a2)

canonicalCompare

public static <U extends Comparable<? super U>> int canonicalCompare(List<? extends U> o1,
                                                                     List<? extends U> o2)

Compares two Lists of Comparable elements with respect to canonical ordering.

In canonical ordering, a sequence o1 is less than a sequence o2 if o1 is shorter than o2, or if they have the same length and o1 is lexicographically smaller than o2.

Parameters:

o1 - the first list

o2 - the second list

Returns:

the result of the comparison

lexCompare

public static <U> int lexCompare(Iterable<? extends U> o1,
                                 Iterable<? extends U> o2,
                                 Comparator<U> elemComparator)

Lexicographically compares two Iterables. Comparison of the elements is done using the specified comparator.

Parameters:

o1 - the first iterable.

o2 - the second iterable.

elemComparator - the comparator.

Returns:

< 0 iff o1 is lexicographically smaller, 0 if o1 equals o2 and > 0 otherwise.

lexCompare

public static int lexCompare(int[] a1,
                             int[] a2)

lexCompare

public static <U extends Comparable<? super U>> int lexCompare(Iterable<? extends U> o1,
                                                               Iterable<? extends U> o2)

Lexicographically compares two Iterables, whose element types are comparable.

lexComparator

public static <T extends Iterable<U>,U> Comparator<T> lexComparator(Comparator<U> elemComp)

Retrieves a lexicographical comparator for the given type.

Parameters:

elemComp - the comparator to use for comparing the elements.

Returns:

a comparator for comparing objects of type T based on lexicographical ordering.

lexComparator

public static <U extends Comparable<U>,T extends Iterable<U>> Comparator<T> lexComparator()

Retrieves a lexicographical comparator for the given type, which has to be an Iterable of Comparable types.

Returns:

the lexicographical comparator.

canonicalComparator

public static <T extends List<? extends U>,U> Comparator<T> canonicalComparator(Comparator<? super U> elemComp)

Retrieves a canonical comparator for the given list type.

Parameters:

elemComp - the comparator to use for comparing the elements.

Returns:

a comparator for comparing objects of type T based on canonical ordering.

canonicalComparator

public static <T extends List<U>,U extends Comparable<U>> Comparator<T> canonicalComparator()

Retrieves a canonical comparator for the given type, which has to be a List of Comparable types.

Returns:

the canonical comparator

See Also:

canonicalCompare(List, List)

safeComparator

public static <T> Comparator<T> safeComparator(Comparator<? super T> baseComp,
                                               CmpUtil.NullOrdering nullOrd)

Retrieves a safe comparator, which can handle null element values. Whether null values are smaller or bigger than regular values is controlled by the CmpUtil.NullOrdering parameter.

Type Parameters:

T - original element class.

Parameters:

baseComp - the basic comparator.

nullOrd - the ordering policy for null values.

Returns:

a safe comparator using the specified underlying comparator.