Package org.apache.calcite.util

Class Pair<T1,T2>

java.lang.Object

org.apache.calcite.util.Pair<T1,T2>

Type Parameters:

T1 - Left-hand type

T2 - Right-hand type

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<Pair<T1,T2>>, java.util.Map.Entry<T1,T2>

Direct Known Subclasses:

Interpreter.Edge, ReflectiveSqlOperatorTable.Key, RelBuilder.Field, RelFieldTrimmer.TrimResult, RexFieldCollation

public class Pair<T1,T2>
extends java.lang.Object
implements java.lang.Comparable<Pair<T1,T2>>, java.util.Map.Entry<T1,T2>, java.io.Serializable

Pair of objects.

Because a pair implements equals(Object), hashCode() and compareTo(Pair), it can be used in any kind of Collection.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	Pair.AdjacentIterator<E>	Iterator that returns consecutive pairs of elements from an underlying iterator.
private static class	Pair.FirstAndIterator<E>	Iterator that returns the first element of a collection paired with every other element.
private static class	Pair.LeftIterator<L,R>	Iterator that returns the left field of each pair.
private static class	Pair.RightIterator<L,R>	Iterator that returns the right field of each pair.
private static class	Pair.ZipIterator<L,R>	Iterator that pairs elements from two iterators.

Field Summary

Fields

Modifier and Type	Field	Description
T1	left
T2	right

Constructor Summary

Constructors

Constructor	Description
Pair(T1 left, T2 right)	Creates a Pair.

Method Summary

Modifier and Type	Method	Description
static <T> java.lang.Iterable<Pair<T,T>>	adjacents(java.lang.Iterable<T> iterable)	Returns an iterator that iterates over (i, i + 1) pairs in an iterable.
private static <C extends java.lang.Comparable<C>> int	compare(C c1, C c2)	Compares a pair of comparable values of the same type.
int	compareTo(Pair<T1,T2> that)
boolean	equals(java.lang.Object obj)
static <T> java.lang.Iterable<Pair<T,T>>	firstAnd(java.lang.Iterable<T> iterable)	Returns an iterator that iterates over (0, i) pairs in an iterable for i > 0.
T1	getKey()
T2	getValue()
int	hashCode()
static <L,R> java.lang.Iterable<L>	left(java.lang.Iterable<? extends java.util.Map.Entry<L,R>> iterable)	Returns an iterable over the left slice of an iterable.
static <K,V> java.util.List<K>	left(java.util.List<? extends java.util.Map.Entry<K,V>> pairs)
static <K,V> Pair<K,V>	of(java.util.Map.Entry<K,V> entry)	Creates a Pair from a Map.Entry.
static <T1,T2> Pair<T1,T2>	of(T1 left, T2 right)	Creates a Pair of appropriate type.
static <L,R> java.lang.Iterable<R>	right(java.lang.Iterable<? extends java.util.Map.Entry<L,R>> iterable)	Returns an iterable over the right slice of an iterable.
static <K,V> java.util.List<V>	right(java.util.List<? extends java.util.Map.Entry<K,V>> pairs)
T2	setValue(T2 value)
static <K,V> java.util.Map<K,V>	toMap(java.lang.Iterable<Pair<K,V>> pairs)	Converts a collection of Pairs into a Map.
java.lang.String	toString()
static <K,V> java.lang.Iterable<Pair<K,V>>	zip(java.lang.Iterable<? extends K> ks, java.lang.Iterable<? extends V> vs)	Converts two iterables into an iterable of Pairs.
static <K,V> java.util.List<Pair<K,V>>	zip(java.util.List<K> ks, java.util.List<V> vs)	Converts two lists into a list of Pairs, whose length is the lesser of the lengths of the source lists.
static <K,V> java.util.List<Pair<K,V>>	zip(java.util.List<K> ks, java.util.List<V> vs, boolean strict)	Converts two lists into a list of Pairs.
static <K,V> java.util.List<Pair<K,V>>	zip(K[] ks, V[] vs)	Converts two arrays into a list of Pairs.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

left

public final T1 left

right

public final T2 right

Constructor Detail

Pair

public Pair(T1 left,
            T2 right)

Creates a Pair.

Parameters:

left - left value

right - right value

Method Detail

of

public static <T1,T2> Pair<T1,T2> of(T1 left,
                                                 T2 right)

Creates a Pair of appropriate type.

This is a shorthand that allows you to omit implicit types. For example, you can write:

return Pair.of(s, n);

instead of

return new Pair<String, Integer>(s, n);

Parameters:

left - left value

right - right value

Returns:

A Pair

of

public static <K,V> Pair<K,V> of(java.util.Map.Entry<K,V> entry)

Creates a Pair from a Map.Entry.

equals

public boolean equals(java.lang.Object obj)

Specified by:

equals in interface java.util.Map.Entry<T1,T2>

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Computes hash code consistent with Map.Entry.hashCode().

Specified by:

hashCode in interface java.util.Map.Entry<T1,T2>

Overrides:

hashCode in class java.lang.Object

compareTo

public int compareTo(@Nonnull
                     Pair<T1,T2> that)

Specified by:

compareTo in interface java.lang.Comparable<T1>

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

getKey

public T1 getKey()

Specified by:

getKey in interface java.util.Map.Entry<T1,T2>

getValue

public T2 getValue()

Specified by:

getValue in interface java.util.Map.Entry<T1,T2>

setValue

public T2 setValue(T2 value)

Specified by:

setValue in interface java.util.Map.Entry<T1,T2>

compare

private static <C extends java.lang.Comparable<C>> int compare(C c1,
                                                               C c2)

Compares a pair of comparable values of the same type. Null collates less than everything else, but equal to itself.

Parameters:

c1 - First value

c2 - Second value

Returns:

a negative integer, zero, or a positive integer if c1 is less than, equal to, or greater than c2.

toMap

public static <K,V> java.util.Map<K,V> toMap(java.lang.Iterable<Pair<K,V>> pairs)

Converts a collection of Pairs into a Map.

This is an obvious thing to do because Pair is similar in structure to Map.Entry.

The map contains a copy of the collection of Pairs; if you change the collection, the map does not change.

Parameters:

pairs - Collection of Pair objects

Returns:

map with the same contents as the collection

zip

public static <K,V> java.util.List<Pair<K,V>> zip(java.util.List<K> ks,
                                                              java.util.List<V> vs)

Converts two lists into a list of Pairs, whose length is the lesser of the lengths of the source lists.

Parameters:

ks - Left list

vs - Right list

Returns:

List of pairs

See Also:

Ord.zip(java.util.List)

zip

public static <K,V> java.util.List<Pair<K,V>> zip(java.util.List<K> ks,
                                                              java.util.List<V> vs,
                                                              boolean strict)

Converts two lists into a list of Pairs.

The length of the combined list is the lesser of the lengths of the source lists. But typically the source lists will be the same length.

Parameters:

ks - Left list

vs - Right list

strict - Whether to fail if lists have different size

Returns:

List of pairs

See Also:

Ord.zip(java.util.List)

zip

public static <K,V> java.lang.Iterable<Pair<K,V>> zip(java.lang.Iterable<? extends K> ks,
                                                                  java.lang.Iterable<? extends V> vs)

Converts two iterables into an iterable of Pairs.

The resulting iterator ends whenever the first of the input iterators ends. But typically the source iterators will be the same length.

Parameters:

ks - Left iterable

vs - Right iterable

Returns:

Iterable over pairs

zip

public static <K,V> java.util.List<Pair<K,V>> zip(K[] ks,
                                                              V[] vs)

Converts two arrays into a list of Pairs.

The length of the combined list is the lesser of the lengths of the source arrays. But typically the source arrays will be the same length.

Parameters:

ks - Left array

vs - Right array

Returns:

List of pairs

left

public static <L,R> java.lang.Iterable<L> left(java.lang.Iterable<? extends java.util.Map.Entry<L,R>> iterable)

Returns an iterable over the left slice of an iterable.

Type Parameters:

L - Left type

R - Right type

Parameters:

iterable - Iterable over pairs

Returns:

Iterable over the left elements

right

public static <L,R> java.lang.Iterable<R> right(java.lang.Iterable<? extends java.util.Map.Entry<L,R>> iterable)

Returns an iterable over the right slice of an iterable.

Type Parameters:

L - right type

R - Right type

Parameters:

iterable - Iterable over pairs

Returns:

Iterable over the right elements

left

public static <K,V> java.util.List<K> left(java.util.List<? extends java.util.Map.Entry<K,V>> pairs)

right

public static <K,V> java.util.List<V> right(java.util.List<? extends java.util.Map.Entry<K,V>> pairs)

adjacents

public static <T> java.lang.Iterable<Pair<T,T>> adjacents(java.lang.Iterable<T> iterable)

Returns an iterator that iterates over (i, i + 1) pairs in an iterable.

For example, adjacents([3, 5, 7]) returns [(3, 5), (5, 7)].

Type Parameters:

T - Element type

Parameters:

iterable - Source collection

Returns:

Iterable over adjacent element pairs

firstAnd

public static <T> java.lang.Iterable<Pair<T,T>> firstAnd(java.lang.Iterable<T> iterable)

Returns an iterator that iterates over (0, i) pairs in an iterable for i > 0.

For example, firstAnd([3, 5, 7]) returns [(3, 5), (3, 7)].

Type Parameters:

T - Element type

Parameters:

iterable - Source collection

Returns:

Iterable over pairs of the first element and all other elements