Package nva.commons.core

Class SingletonCollector

java.lang.Object

nva.commons.core.SingletonCollector

public final class SingletonCollector
extends Object

Field Summary

Fields

Modifier and Type	Field	Description
static final int	ONLY_ELEMENT
static final int	SINGLETON
static final String	SINGLETON_EXPECTED_ERROR_TEMPLATE
static final String	SINGLETON_OR_NULL_EXPECTED_ERROR_TEMPLATE

Method Summary

Modifier and Type	Method	Description
static <T> Collector<T,?,T>	collect()	A utility to collect and return singletons from lists.
static <T> Collector<T,?,T>	collectOrElse(T alternative)	Returns the single expected value in the Stream or the alternative if nothing was found.
static <T, E extends Exception> Collector<T,?,Try<T>>	tryCollect()	A utility to return a singleton from a list that is expected to contain one and only one item, throwing supplied exception if the list is empty or does not contain one element.

Methods inherited from class java.lang.Object

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

Field Details

SINGLETON

public static final int SINGLETON

See Also:

• Constant Field Values

ONLY_ELEMENT

public static final int ONLY_ELEMENT

See Also:

• Constant Field Values

SINGLETON_EXPECTED_ERROR_TEMPLATE

public static final String SINGLETON_EXPECTED_ERROR_TEMPLATE

See Also:

• Constant Field Values

SINGLETON_OR_NULL_EXPECTED_ERROR_TEMPLATE

public static final String SINGLETON_OR_NULL_EXPECTED_ERROR_TEMPLATE

See Also:

• Constant Field Values

Method Details

collect

public static <T> Collector<T,?,T> collect()

A utility to collect and return singletons from lists.

Type Parameters:

T - the type of input elements to the reduction operation.

Returns:

a singleton of type T.

collectOrElse

public static <T> Collector<T,?,T> collectOrElse(T alternative)

Returns the single expected value in the Stream or the alternative if nothing was found. It throws an IllegalStateException when more than one results have been collected from the Stream

Type Parameters:

T - the class of the collected object.

Parameters:

alternative - the alterative value if the Stream is empty.

Returns:

the single value of the Stream or the alternative if the Stream is empty.

tryCollect

public static <T,
E extends Exception>
Collector<T,?,Try<T>> tryCollect()

A utility to return a singleton from a list that is expected to contain one and only one item, throwing supplied exception if the list is empty or does not contain one element.

Type Parameters:

T - The type of input elements to the reduction operation.

E - The type of the exception to be thrown.

Returns:

A type of the singleton.