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:

Serializable, Comparable<Pair<T1,T2>>, Map.Entry<T1,T2>

Direct Known Subclasses:

RelFieldTrimmer.TrimResult, RexFieldCollation

public class Pair<T1,T2>
extends Object
implements Comparable<Pair<T1,T2>>, Map.Entry<T1,T2>, 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

Field Summary

Fields

Modifier and Type	Field and Description
T1	left
T2	right

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
static <T> Iterable<Pair<T,T>>	adjacents(Iterable<? extends T> iterable) Returns an iterator that iterates over (i, i + 1) pairs in an iterable.
int	compareTo(Pair<T1,T2> that)
boolean	equals(@Nullable Object obj)
static <T> Iterable<Pair<T,T>>	firstAnd(Iterable<? extends T> iterable) Returns an iterator that iterates over (0, i) pairs in an iterable for i > 0.
static <K,V> void	forEach(Iterable<? extends K> ks, Iterable<? extends V> vs, BiConsumer<? super K,? super V> consumer) Applies an action to every element of a pair of iterables.
static <K,V> void	forEach(Iterable<? extends Map.Entry<? extends K,? extends V>> entries, BiConsumer<? super K,? super V> consumer) Applies an action to every element of an iterable of pairs.
T1	getKey()
T2	getValue()
int	hashCode()
static <L,R> Iterable<L>	left(Iterable<? extends Map.Entry<? extends L,? extends R>> iterable) Returns an iterable over the left slice of an iterable.
static <K,V> List<K>	left(List<? extends Map.Entry<? extends K,? extends V>> pairs)
static <K,V> Pair<K,V>	of(Map.Entry<? extends K,? extends 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> Iterable<R>	right(Iterable<? extends Map.Entry<? extends L,? extends R>> iterable) Returns an iterable over the right slice of an iterable.
static <K,V> List<V>	right(List<? extends Map.Entry<? extends K,? extends V>> pairs)
T2	setValue(T2 value)
static <K,V> Map<K,V>	toMap(Iterable<? extends Pair<? extends K,? extends V>> pairs) Converts a collection of Pairs into a Map.
String	toString()
static <K,V> Iterable<Pair<K,V>>	zip(Iterable<? extends K> ks, Iterable<? extends V> vs) Converts two iterables into an iterable of Pairs.
static <K,V> List<Pair<K,V>>	zip(K[] ks, V[] vs) Converts two arrays into a list of Pairs.
static <K,V> List<Pair<K,V>>	zip(List<? extends K> ks, List<? extends 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> List<Pair<K,V>>	zip(List<? extends K> ks, List<? extends V> vs, boolean strict) Converts two lists into a list of Pairs.
static <K,V> List<Pair<K,V>>	zipMutable(List<K> ks, List<V> vs) Returns a mutable list of pairs backed by a pair of mutable lists.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map.Entry

comparingByKey, comparingByKey, comparingByValue, comparingByValue

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(Map.Entry<? extends K,? extends V> entry)

Creates a Pair from a Map.Entry.

equals

public boolean equals(@Nullable Object obj)

Specified by:

equals in interface Map.Entry<T1,T2>

Overrides:

equals in class Object

hashCode

public int hashCode()

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

Specified by:

hashCode in interface Map.Entry<T1,T2>

Overrides:

hashCode in class Object

compareTo

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

Specified by:

compareTo in interface Comparable<Pair<T1,T2>>

toString

public String toString()

Overrides:

toString in class Object

getKey

public T1 getKey()

Specified by:

getKey in interface Map.Entry<T1,T2>

getValue

public T2 getValue()

Specified by:

getValue in interface Map.Entry<T1,T2>

setValue

public T2 setValue(T2 value)

Specified by:

setValue in interface Map.Entry<T1,T2>

toMap

public static <K,V> Map<K,V> toMap(Iterable<? extends Pair<? extends K,? extends 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> List<Pair<K,V>> zip(List<? extends K> ks,
                                        List<? extends 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> List<Pair<K,V>> zip(List<? extends K> ks,
                                        List<? extends 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> Iterable<Pair<K,V>> zip(Iterable<? extends K> ks,
                                            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> 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

zipMutable

public static <K,V> List<Pair<K,V>> zipMutable(List<K> ks,
                                               List<V> vs)

Returns a mutable list of pairs backed by a pair of mutable lists.

Modifications to this list are reflected in the backing lists, and vice versa.

Type Parameters:

K - Key (left) value type

V - Value (right) value type

forEach

public static <K,V> void forEach(Iterable<? extends K> ks,
                                 Iterable<? extends V> vs,
                                 BiConsumer<? super K,? super V> consumer)

Applies an action to every element of a pair of iterables.

Calls to the action stop whenever the first of the input iterators ends. But typically the source iterators will be the same length.

Type Parameters:

K - Left type

V - Right type

Parameters:

ks - Left iterable

vs - Right iterable

consumer - The action to be performed for each element

See Also:

Map.forEach(java.util.function.BiConsumer), Ord.forEach(Iterable, java.util.function.ObjIntConsumer)

forEach

public static <K,V> void forEach(Iterable<? extends Map.Entry<? extends K,? extends V>> entries,
                                 BiConsumer<? super K,? super V> consumer)

Applies an action to every element of an iterable of pairs.

Type Parameters:

K - Left type

V - Right type

Parameters:

entries - Pairs

consumer - The action to be performed for each element

See Also:

Map.forEach(java.util.function.BiConsumer)

left

public static <L,R> Iterable<L> left(Iterable<? extends Map.Entry<? extends L,? extends 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> Iterable<R> right(Iterable<? extends Map.Entry<? extends L,? extends 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> List<K> left(List<? extends Map.Entry<? extends K,? extends V>> pairs)

right

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

adjacents

public static <T> Iterable<Pair<T,T>> adjacents(Iterable<? extends 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> Iterable<Pair<T,T>> firstAnd(Iterable<? extends 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