Linq4j (Apache Calcite API)

java.lang.Object
- org.apache.calcite.linq4j.Linq4j

public abstract class Linq4j
extends Object

Utility and factory methods for Linq4j.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`private static class`	`Linq4j.CartesianProductListEnumerator<E>` Enumerates over the cartesian product of the given lists, returning a list for each row.
`(package private) static class`	`Linq4j.CollectionEnumerable<T>` Collection enumerable.
`(package private) static class`	`Linq4j.CompositeEnumerable<E>` Composite enumerable.
`private static class`	`Linq4j.EnumeratorIterator<T>` Iterator that reads from an underlying `Enumerator`.
`(package private) static class`	`Linq4j.IterableEnumerable<T>` Iterable enumerable.
`(package private) static class`	`Linq4j.IterableEnumerator<T>` Iterable enumerator.
`(package private) static class`	`Linq4j.ListEnumerable<T>` List enumerable.
`private static class`	`Linq4j.ListEnumerator<V>` Enumerator optimized for random-access list.
`private static class`	`Linq4j.SingletonEnumerator<E>` Enumerator that returns one element.
`private static class`	`Linq4j.SingletonNullEnumerator<E>` Enumerator that returns one null element.

Field Summary

Fields
Modifier and Type	Field and Description
`static QueryProvider`	`DEFAULT_PROVIDER` Query provider that simply executes a `Queryable` by calling its enumerator method; does not attempt optimization.
`private static Object`	`DUMMY`
`static Enumerable<?>`	`EMPTY_ENUMERABLE`
`private static Enumerator<Object>`	`EMPTY_ENUMERATOR`

Constructor Summary

Constructors
Modifier Constructor and Description

private Linq4j()

Constructors
Modifier	Constructor and Description
`private`	`Linq4j()`

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`static <T> Enumerable<T>`	`asEnumerable(Collection<T> collection)` Adapter that converts an `Collection` into an `Enumerable`.
`static <T> Enumerable<T>`	`asEnumerable(Iterable<T> iterable)` Adapter that converts an `Iterable` into an `Enumerable`.
`static <T> Enumerable<T>`	`asEnumerable(List<T> list)` Adapter that converts an `List` into an `Enumerable`.
`static <T> Enumerable<T>`	`asEnumerable(T[] ts)` Adapter that converts an array into an enumerable.
`static <TSource,TResult> Enumerable<TResult>`	`cast(Iterable<TSource> source, Class<TResult> clazz)` Converts the elements of a given Iterable to the specified type.
`private static <T> void`	`closeIterator(Iterator<T> iterator)` Closes an iterator, if it can be closed.
`static <E> Enumerable<E>`	`concat(List<Enumerable<E>> enumerableList)` Concatenates two or more `Enumerable`s to form a composite enumerable that contains the union of their elements.
`static <T> Enumerable<T>`	`emptyEnumerable()` Returns an `Enumerable` that has no elements.
`static <T> Enumerator<T>`	`emptyEnumerator()` Returns an `Enumerator` that has no elements.
`static <V> Enumerator<V>`	`enumerator(Collection<? extends V> values)` Adapter that converts a collection into an enumerator.
`static <T> Iterator<T>`	`enumeratorIterator(Enumerator<T> enumerator)` Adapter that converts an enumerator into an iterator.
`static <T> boolean`	`equals(T t0, T t1)` Deprecated.
`static Method`	`getMethod(String className, String methodName, Class... parameterTypes)`
`static <T> Enumerator<T>`	`iterableEnumerator(Iterable<? extends T> iterable)` Adapter that converts an iterable into an enumerator.
`private static <V> Enumerator<V>`	`listEnumerator(List<? extends V> list)`
`static <TSource,TResult> Enumerable<TResult>`	`ofType(Iterable<TSource> source, Class<TResult> clazz)` Returns elements of a given `Iterable` that are of the specified type.
`static <T> Iterable<List<T>>`	`product(Iterable<? extends Iterable<T>> iterables)` Returns the cartesian product of an iterable of iterables.
`static <T> Enumerator<List<T>>`	`product(List<Enumerator<T>> enumerators)` Returns an enumerator that is the cartesian product of the given enumerators.
`static <T> T`	`requireNonNull(T o)` Deprecated.
`static <T> Enumerable<T>`	`singletonEnumerable(T element)` Returns an `Enumerable` that has one element.
`static <T> Enumerator<T>`	`singletonEnumerator(T element)` Returns an `Enumerator` that has one element.
`static <T> Enumerator<T>`	`singletonNullEnumerator()` Returns an `Enumerator` that has one null element.
`static <F,E> Enumerator<E>`	`transform(Enumerator<F> enumerator, Function1<F,E> func)` Applies a function to each element of an Enumerator.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - DUMMY
```
private static final Object DUMMY
```
  - DEFAULT_PROVIDER
```
public static final QueryProvider DEFAULT_PROVIDER
```
    Query provider that simply executes a Queryable by calling its enumerator method; does not attempt optimization.
  - EMPTY_ENUMERATOR
```
private static final Enumerator<Object> EMPTY_ENUMERATOR
```
  - EMPTY_ENUMERABLE
```
public static final Enumerable<?> EMPTY_ENUMERABLE
```
- Constructor Detail
  - Linq4j
```
private Linq4j()
```
- Method Detail
  - getMethod
```
public static Method getMethod(String className,
                               String methodName,
                               Class... parameterTypes)
```
  - enumeratorIterator
```
public static <T> Iterator<T> enumeratorIterator(Enumerator<T> enumerator)
```
    Adapter that converts an enumerator into an iterator.
    WARNING: The iterator returned by this method does not call Enumerator.close(), so it is not safe to use with an enumerator that allocates resources.
    
    Type Parameters:
    
    T - Element type
    
    Parameters:
    
    enumerator - Enumerator
    
    Returns:
    
    Iterator
  - iterableEnumerator
```
public static <T> Enumerator<T> iterableEnumerator(Iterable<? extends T> iterable)
```
    Adapter that converts an iterable into an enumerator.
    
    Type Parameters:
    
    T - Element type
    
    Parameters:
    
    iterable - Iterable
    
    Returns:
    
    enumerator
  - asEnumerable
```
public static <T> Enumerable<T> asEnumerable(List<T> list)
```
    Adapter that converts an List into an Enumerable.
    
    Type Parameters:
    
    T - Element type
    
    Parameters:
    
    list - List
    
    Returns:
    
    enumerable
  - asEnumerable
```
public static <T> Enumerable<T> asEnumerable(Collection<T> collection)
```
    Adapter that converts an Collection into an Enumerable.
    It uses more efficient implementations if the iterable happens to be a List.
    
    Type Parameters:
    
    T - Element type
    
    Parameters:
    
    collection - Collection
    
    Returns:
    
    enumerable
  - asEnumerable
```
public static <T> Enumerable<T> asEnumerable(Iterable<T> iterable)
```
    Adapter that converts an Iterable into an Enumerable.
    It uses more efficient implementations if the iterable happens to be a Collection or a List.
    
    Type Parameters:
    
    T - Element type
    
    Parameters:
    
    iterable - Iterable
    
    Returns:
    
    enumerable
  - asEnumerable
```
public static <T> Enumerable<T> asEnumerable(T[] ts)
```
    Adapter that converts an array into an enumerable.
    
    Type Parameters:
    
    T - Element type
    
    Parameters:
    
    ts - Array
    
    Returns:
    
    enumerable
  - enumerator
```
public static <V> Enumerator<V> enumerator(Collection<? extends V> values)
```
    Adapter that converts a collection into an enumerator.
    
    Type Parameters:
    
    V - Element type
    
    Parameters:
    
    values - Collection
    
    Returns:
    
    Enumerator over the collection
  - listEnumerator
```
private static <V> Enumerator<V> listEnumerator(List<? extends V> list)
```
  - transform
```
public static <F,E> Enumerator<E> transform(Enumerator<F> enumerator,
                                            Function1<F,E> func)
```
    Applies a function to each element of an Enumerator.
    
    Type Parameters:
    
    F - Backing element type
    
    E - Element type
    
    Parameters:
    
    enumerator - Backing enumerator
    
    func - Transform function
    
    Returns:
    
    Enumerator
  - cast
```
public static <TSource,TResult> Enumerable<TResult> cast(Iterable<TSource> source,
                                                         Class<TResult> clazz)
```
    Converts the elements of a given Iterable to the specified type.
    This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its RawEnumerable.enumerator() method directly or by using for (... in ...).
    Since standard Java Collection objects implement the Iterable interface, the cast method enables the standard query operators to be invoked on collections (including List and Set) by supplying the necessary type information. For example, ArrayList does not implement Enumerable<F>, but you can invoke
    Linq4j.cast(list, Integer.class)
    
    to convert the list of an enumerable that can be queried using the standard query operators.
    If an element cannot be cast to type <TResult>, this method will throw a ClassCastException. To obtain only those elements that can be cast to type TResult, use the ofType(java.lang.Iterable<TSource>, java.lang.Class<TResult>) method instead.
    
    See Also:
    
    ExtendedEnumerable.cast(Class), ofType(java.lang.Iterable<TSource>, java.lang.Class<TResult>), asEnumerable(Iterable)
  - ofType
```
public static <TSource,TResult> Enumerable<TResult> ofType(Iterable<TSource> source,
                                                           Class<TResult> clazz)
```
    Returns elements of a given Iterable that are of the specified type.
    This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its RawEnumerable.enumerator() method directly or by using for (... in ...).
    The ofType method returns only those elements in source that can be cast to type TResult. To instead receive an exception if an element cannot be cast to type TResult, use cast(Iterable, Class).
    
    Since standard Java Collection objects implement the Iterable interface, the cast method enables the standard query operators to be invoked on collections (including List and Set) by supplying the necessary type information. For example, ArrayList does not implement Enumerable<F>, but you can invoke
    Linq4j.ofType(list, Integer.class)
    
    to convert the list of an enumerable that can be queried using the standard query operators.
    
    See Also:
    
    ExtendedEnumerable.cast(Class), cast(java.lang.Iterable<TSource>, java.lang.Class<TResult>)
  - singletonEnumerable
```
public static <T> Enumerable<T> singletonEnumerable(T element)
```
    Returns an Enumerable that has one element.
    
    Type Parameters:
    
    T - Element type
    
    Returns:
    
    Singleton enumerable
  - singletonEnumerator
```
public static <T> Enumerator<T> singletonEnumerator(T element)
```
    Returns an Enumerator that has one element.
    
    Type Parameters:
    
    T - Element type
    
    Returns:
    
    Singleton enumerator
  - singletonNullEnumerator
```
public static <T> Enumerator<T> singletonNullEnumerator()
```
    Returns an Enumerator that has one null element.
    
    Type Parameters:
    
    T - Element type
    
    Returns:
    
    Singleton enumerator
  - emptyEnumerable
```
public static <T> Enumerable<T> emptyEnumerable()
```
    Returns an Enumerable that has no elements.
    
    Type Parameters:
    
    T - Element type
    
    Returns:
    
    Empty enumerable
  - emptyEnumerator
```
public static <T> Enumerator<T> emptyEnumerator()
```
    Returns an Enumerator that has no elements.
    
    Type Parameters:
    
    T - Element type
    
    Returns:
    
    Empty enumerator
  - concat
```
public static <E> Enumerable<E> concat(List<Enumerable<E>> enumerableList)
```
    Concatenates two or more Enumerables to form a composite enumerable that contains the union of their elements.
    
    Type Parameters:
    
    E - Element type
    
    Parameters:
    
    enumerableList - List of enumerable objects
    
    Returns:
    
    Composite enumerator
  - product
```
public static <T> Enumerator<List<T>> product(List<Enumerator<T>> enumerators)
```
    Returns an enumerator that is the cartesian product of the given enumerators.
    For example, given enumerator A that returns {"a", "b", "c"} and enumerator B that returns {"x", "y"}, product(List(A, B)) will return {List("a", "x"), List("a", "y"), List("b", "x"), List("b", "y"), List("c", "x"), List("c", "y")}.
    
    Notice that the cardinality of the result is the product of the cardinality of the inputs. The enumerators A and B have 3 and 2 elements respectively, and the result has 3 * 2 = 6 elements. This is always the case. In particular, if any of the enumerators is empty, the result is empty.
    
    Type Parameters:
    
    T - Element type
    
    Parameters:
    
    enumerators - List of enumerators
    
    Returns:
    
    Enumerator over the cartesian product
  - product
```
public static <T> Iterable<List<T>> product(Iterable<? extends Iterable<T>> iterables)
```
    Returns the cartesian product of an iterable of iterables.
  - equals
```
@Deprecated
public static <T> boolean equals(T t0,
                                             T t1)
```
    Deprecated.
    
    Returns whether the arguments are equal to each other.
    Equivalent to Objects.equals(java.lang.Object, java.lang.Object) in JDK 1.7 and above.
  - requireNonNull
```
@Deprecated
public static <T> T requireNonNull(T o)
```
    Deprecated.
    
    Throws NullPointerException if argument is null, otherwise returns argument.
    Equivalent to Objects.requireNonNull(T) in JDK 1.7 and above.
  - closeIterator
```
private static <T> void closeIterator(Iterator<T> iterator)
```
    Closes an iterator, if it can be closed.

Class Linq4j

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

DUMMY

DEFAULT_PROVIDER

EMPTY_ENUMERATOR

EMPTY_ENUMERABLE

Constructor Detail

Linq4j

Method Detail

getMethod

enumeratorIterator

iterableEnumerator

asEnumerable

asEnumerable

asEnumerable

asEnumerable

enumerator

listEnumerator

transform

cast

ofType

singletonEnumerable

singletonEnumerator

singletonNullEnumerator

emptyEnumerable

emptyEnumerator

concat

product

product

equals

requireNonNull

closeIterator