Module org.microbean.invoke

Package org.microbean.invoke

Class CachingSupplier<T>

java.lang.Object

org.microbean.invoke.CachingSupplier<T>

Type Parameters:

T - The type of object returned by the get() method

All Implemented Interfaces:

Supplier<T>, OptionalSupplier<T>

public final class CachingSupplier<T>
extends Object
implements OptionalSupplier<T>

An OptionalSupplier that computes the value it will return from its get() method when that method is first invoked, and that returns that computed value for all subsequent invocations of that method.

Author:

Laird Nelson

See Also:

• CachingSupplier(Object)
• CachingSupplier(Supplier)
• get()
• set(Object)

Nested Class Summary

Nested classes/interfaces inherited from interface org.microbean.invoke.OptionalSupplier

OptionalSupplier.Determinism

Constructor Summary

Constructors

Constructor	Description
CachingSupplier()	Creates a new CachingSupplier.
CachingSupplier(Supplier<? extends T> supplier)	Creates a new CachingSupplier.
CachingSupplier(T value)	Creates a new CachingSupplier.

Method Summary

Modifier and Type	Method	Description
final OptionalSupplier.Determinism	determinism()	Returns an OptionalSupplier.Determinism suitable for this CachingSupplier.
final T	get()	Returns the value this CachingSupplier will forever supply, computing it if necessary with the first invocation by using the Supplier supplied at construction time.
final boolean	set(T newValue)	Sets the value that will be returned forever afterwards by the get() method and returns true if and only if the value was previously unset.
final String	toString()	Returns a non-null String representation of this CachingSupplier.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.microbean.invoke.OptionalSupplier

exceptionally, handle, ifPresent, ifPresentOrElse, optional, optional, optional, orElse, orElseGet, orElseThrow, orElseThrow, stream

Constructor Details

CachingSupplier

public CachingSupplier()

Creates a new CachingSupplier.

See Also:

• CachingSupplier(Supplier)
• get()
• set(Object)
• AtomicReference.updateAndGet(java.util.function.UnaryOperator)

CachingSupplier

public CachingSupplier(T value)

Creates a new CachingSupplier.

An invocation of this constructor will result in the set(Object) method always returning false.

Parameters:

value - the value that will be returned by all invocations of the get() method; may be null in which case the get() method will return null forever

See Also:

• get()

CachingSupplier

public CachingSupplier(Supplier<? extends T> supplier)

Creates a new CachingSupplier.

Parameters:

supplier - the Supplier that will be used to supply the value that will be returned by all invocations of the get() method; may be null in which case the get() method will throw a NoSuchElementException until, at least, the set(Object) method is called; must be safe for concurrent use by multiple threads and must be side-effect free

See Also:

• get()

Method Details

get

public final T get()

Returns the value this CachingSupplier will forever supply, computing it if necessary with the first invocation by using the Supplier supplied at construction time.

If the Supplier supplied at construction time returns null from its Supplier.get() method, then this method will forever return null as well.

Specified by:

get in interface OptionalSupplier<T>

Specified by:

get in interface Supplier<T>

Returns:

the value, which may very well be null

See Also:

• CachingSupplier(Object)
• CachingSupplier(Supplier)
• set(Object)

Idempotency:

This method's idempotency and determinism are determined by the idempotency and determinisim of the Supplier supplied at construction time.

Nullability:

This method may return null.

Thread Safety:

This method is safe for concurrent use by multiple threads.

set

public final boolean set(T newValue)

Sets the value that will be returned forever afterwards by the get() method and returns true if and only if the value was previously unset.

Parameters:

newValue - the new value that will be returned by the get() method forever afterwards; may be null

Returns:

true if and only if this assignment was permitted; false otherwise

See Also:

• get()
• CachingSupplier(Supplier)
• AtomicReference.compareAndSet(Object, Object)

Idempotency:

This method is idempotent but not deterministic.

Thread Safety:

This method is safe for concurrent use by multiple threads.

determinism

public final OptionalSupplier.Determinism determinism()

Returns an OptionalSupplier.Determinism suitable for this CachingSupplier.

In most cases, this method returns OptionalSupplier.Determinism.PRESENT. In the case that the zero-argument constructor was invoked, and the set(Object) method has not yet been called, this method will return OptionalSupplier.Determinism.DETERMINISTIC. Once the set(Object) method has been called, this method will return OptionalSupplier.Determinism.PRESENT.

Specified by:

determinism in interface OptionalSupplier<T>

Returns:

one of OptionalSupplier.Determinism.PRESENT or OptionalSupplier.Determinism.DETERMINISTIC

Idempotency:

This method is idempotent and deterministic.

Nullability:

This method does not return null.

Thread Safety:

This method is safe for concurrent use by multiple threads.

toString

public final String toString()

Returns a non-null String representation of this CachingSupplier.

The format of the return value is deliberately unspecified and subject to change without notice from version to version of this class.

Overrides:

toString in class Object

Returns:

a String representation of this CachingSupplier

Idempotency:

This method is idempotent but not deterministic until a value has been supplied, either via the CachingSupplier(Object) or CachingSupplier(Supplier) constructors or the set(Object) method.

Nullability:

This method never returns null.

Thread Safety:

This method is safe for concurrent use by multiple threads.