com.codepoetics.protonpack.collectors

Class CollectorUtils

java.lang.Object

com.codepoetics.protonpack.collectors.CollectorUtils

public final class CollectorUtils
extends java.lang.Object

Utility class providing some collectors.

Method Summary

Modifier and Type	Method and Description
static <T,Y extends java.lang.Comparable<Y>> java.util.stream.Collector<T,?,java.util.Optional<T>>	maxBy(java.util.function.Function<T,Y> projection) Find the item for which the supplied projection returns the maximum value.
static <T,Y> java.util.stream.Collector<T,?,java.util.Optional<T>>	maxBy(java.util.function.Function<T,Y> projection, java.util.Comparator<Y> comparator) Find the item for which the supplied projection returns the maximum value (variant for non-naturally-comparable projected values).
static <T,Y extends java.lang.Comparable<Y>> java.util.stream.Collector<T,?,java.util.Optional<T>>	minBy(java.util.function.Function<T,Y> projection) Find the item for which the supplied projection returns the minimum value.
static <T,Y> java.util.stream.Collector<T,?,java.util.Optional<T>>	minBy(java.util.function.Function<T,Y> projection, java.util.Comparator<Y> comparator) Find the item for which the supplied projection returns the minimum value (variant for non-naturally-comparable projected values).
static <T> java.util.function.BinaryOperator<T>	noCombiner() A combiner for all the cases when you don't intend to reduce/collect on a parallel stream.
static <T> java.util.stream.Collector<T,java.util.concurrent.atomic.AtomicReference<T>,java.util.Optional<T>>	unique() A collector that returns the single member of a stream (if present), or throws a NonUniqueValueException if more than one item is found.

Methods inherited from class java.lang.Object

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

Method Detail

maxBy

public static <T,Y extends java.lang.Comparable<Y>> java.util.stream.Collector<T,?,java.util.Optional<T>> maxBy(java.util.function.Function<T,Y> projection)

Find the item for which the supplied projection returns the maximum value.

Type Parameters:

T - The type of each item.

Y - The type of the projected value to compare on.

Parameters:

projection - The projection to apply to each item.

Returns:

The collector.

maxBy

public static <T,Y> java.util.stream.Collector<T,?,java.util.Optional<T>> maxBy(java.util.function.Function<T,Y> projection,
                                                                                java.util.Comparator<Y> comparator)

Find the item for which the supplied projection returns the maximum value (variant for non-naturally-comparable projected values).

Type Parameters:

T - The type of each item.

Y - The type of the projected value to compare on.

Parameters:

projection - The projection to apply to each item.

comparator - The comparator to use to compare the projected values.

Returns:

The collector.

minBy

public static <T,Y extends java.lang.Comparable<Y>> java.util.stream.Collector<T,?,java.util.Optional<T>> minBy(java.util.function.Function<T,Y> projection)

Find the item for which the supplied projection returns the minimum value.

Type Parameters:

T - The type of each item.

Y - The type of the projected value to compare on.

Parameters:

projection - The projection to apply to each item.

Returns:

The collector.

minBy

public static <T,Y> java.util.stream.Collector<T,?,java.util.Optional<T>> minBy(java.util.function.Function<T,Y> projection,
                                                                                java.util.Comparator<Y> comparator)

Find the item for which the supplied projection returns the minimum value (variant for non-naturally-comparable projected values).

Type Parameters:

T - The type of each item.

Y - The type of the projected value to compare on.

Parameters:

projection - The projection to apply to each item.

comparator - The comparator to use to compare the projected values.

Returns:

The collector.

unique

public static <T> java.util.stream.Collector<T,java.util.concurrent.atomic.AtomicReference<T>,java.util.Optional<T>> unique()

A collector that returns the single member of a stream (if present), or throws a NonUniqueValueException if more than one item is found.

Type Parameters:

T - The type of the items in the stream.

Returns:

The collector.

noCombiner

public static <T> java.util.function.BinaryOperator<T> noCombiner()

A combiner for all the cases when you don't intend to reduce/collect on a parallel stream. Will throw an IllegalStateException if it is ever called.

Type Parameters:

T - The type of partial result you don't intend to combine.

Returns:

A combiner that throws an exception instead of combining.