org.perro.functions.comparator

Class ComparatorUtils

java.lang.Object

org.perro.functions.comparator.ComparatorUtils

public final class ComparatorUtils
extends java.lang.Object

Methods that build comparators useful in many different situations, particularly in Java streams.

Method Summary

Modifier and Type	Method and Description
static <T extends java.lang.Comparable<T>> java.util.Comparator<T>	comparingNullsFirst() Builds a comparator that can be used to compare and sort instances of any type that extends Comparable.
static <T,R extends java.lang.Comparable<R>> java.util.Comparator<T>	comparingNullsFirst(java.util.function.Function<? super T,? extends R> keyExtractor) Builds a comparator that can be used to compare and sort instances of any type, provided that the keyExtractor function retrieves an instance of Comparable from them.
static <T extends java.lang.Comparable<T>> java.util.Comparator<T>	comparingNullsLast() Builds a comparator that can be used to compare and sort instances of any type that extends Comparable.
static <T,R extends java.lang.Comparable<R>> java.util.Comparator<T>	comparingNullsLast(java.util.function.Function<? super T,? extends R> keyExtractor) Builds a comparator that can be used to compare and sort instances of any type, provided that the keyExtractor function retrieves an instance of Comparable from them.

Methods inherited from class java.lang.Object

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

Method Detail

comparingNullsFirst

public static <T extends java.lang.Comparable<T>> java.util.Comparator<T> comparingNullsFirst()

Builds a comparator that can be used to compare and sort instances of any type that extends Comparable. The comparator sorts in a way that null values come before all non-null ones.

Type Parameters:

T - The type of the elements to be compared, extending the Comparable interface.

Returns:

A comparator of instances of type <T>.

comparingNullsFirst

public static <T,R extends java.lang.Comparable<R>> java.util.Comparator<T> comparingNullsFirst(java.util.function.Function<? super T,? extends R> keyExtractor)

Builds a comparator that can be used to compare and sort instances of any type, provided that the keyExtractor function retrieves an instance of Comparable from them. The comparator sorts in a way that null values come before all non-null ones. Note that, because this method takes a function as its first parameter, that any of the function building methods from MapperUtils are fair game here.

Type Parameters:

T - The type of the elements to be compared.

R - The type of the key value to be extracted, which must extend the Comparable interface.

Parameters:

keyExtractor - An extractor function that retrieves a key value from a target element, the value being an instance of Comparable, which will be compared based on its natural order, with nulls being evaluated as less than non-nulls.

Returns:

A comparator of instances of type <T>.

comparingNullsLast

public static <T extends java.lang.Comparable<T>> java.util.Comparator<T> comparingNullsLast()

Builds a comparator that can be used to compare and sort instances of any type that extends Comparable. The comparator sorts in a way that null values come after all non-null ones.

Type Parameters:

T - The type of the elements to be compared, extending the Comparable interface.

Returns:

A comparator of instances of type <T>.

comparingNullsLast

public static <T,R extends java.lang.Comparable<R>> java.util.Comparator<T> comparingNullsLast(java.util.function.Function<? super T,? extends R> keyExtractor)

Builds a comparator that can be used to compare and sort instances of any type, provided that the keyExtractor function retrieves an instance of Comparable from them. The comparator sorts in a way that null values come after all non-null ones. Note that, because this method takes a function as its first parameter, that any of the function building methods from MapperUtils are fair game here.

Type Parameters:

T - The type of the elements to be compared.

R - The type of the key value to be extracted, which must extend the Comparable interface.

Parameters:

keyExtractor - An extractor function that retrieves a key value from a target element, the value being an instance of Comparable, which will be compared based on its natural order, with nulls being evaluated as greater than non-nulls.

Returns:

A comparator of instances of type <T>.