Package org.apache.calcite.util

Class Holder<E>

java.lang.Object

org.apache.calcite.util.Holder<E>

Type Parameters:

E - Element type

public class Holder<E>
extends Object

A mutable slot that can contain one object.

A holder is useful for implementing OUT or IN-OUT parameters.

It is possible to sub-class to receive events on get or set.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Holder(E e)	Creates a Holder containing a given value.

Method Summary

Modifier and Type	Method	Description
Holder<E>	accept(UnaryOperator<E> transform)	Applies a transform to the value.
static <E> Holder<@Nullable E>	empty()	Creates a holder containing null.
E	get()	Gets the value.
static <E> Holder<E>	of(E e)	Creates a holder containing a given value.
void	set(E e)	Sets the value.

Methods inherited from class java.lang.Object

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

Constructor Details

Holder

protected Holder(E e)

Creates a Holder containing a given value.

Call this method from a derived constructor or via the of(E) method.

Method Details

set

public void set(E e)

Sets the value.

get

public E get()

Gets the value.

accept

public Holder<E> accept(UnaryOperator<E> transform)

Applies a transform to the value.

of

public static <E> Holder<E> of(E e)

Creates a holder containing a given value.

empty

public static <E> Holder<@Nullable E> empty()

Creates a holder containing null.