Package com.google.common.collect

Class Comparators

  • @Beta
@GwtCompatible
public final class Comparators
extends Object
    Provides static methods for working with Comparator instances. For many other helpful comparator utilities, see either Comparator itself (for Java 8 or later), or com.google.common.collect.Ordering (otherwise).

    Relationship to Ordering

    In light of the significant enhancements to Comparator in Java 8, the overwhelming majority of usages of Ordering can be written using only built-in JDK APIs. This class is intended to "fill the gap" and provide those features of Ordering not already provided by the JDK.

    Since:
    21.0
    Author:
    Louis Wasserman

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static <T> boolean isInOrder​(Iterable<? extends T> iterable, Comparator<T> comparator)
      Returns true if each element in iterable after the first is greater than or equal to the element that preceded it, according to the specified comparator.
      static <T> boolean isInStrictOrder​(Iterable<? extends T> iterable, Comparator<T> comparator)
      Returns true if each element in iterable after the first is strictly greater than the element that preceded it, according to the specified comparator.
      static <T,​S extends T>
      Comparator<Iterable<S>>      		 lexicographical​(Comparator<T> comparator)
      Returns a new comparator which sorts iterables by comparing corresponding elements pairwise until a nonzero result is found; imposes "dictionary order." If the end of one iterable is reached, but not the other, the shorter iterable is considered to be less than the longer one.
      static <T extends Comparable<? super T>>
      T      		 max​(T a, T b)
      Returns the maximum of the two values.
      static <T> T max​(T a, T b, Comparator<T> comparator)
      Returns the maximum of the two values, according to the given comparator.
      static <T extends Comparable<? super T>>
      T      		 min​(T a, T b)
      Returns the minimum of the two values.
      static <T> T min​(T a, T b, Comparator<T> comparator)
      Returns the minimum of the two values, according to the given comparator.

    • Method Detail

      • lexicographical

        public static <T,​S extends T> Comparator<Iterable<S>> lexicographical​(Comparator<T> comparator)
        Returns a new comparator which sorts iterables by comparing corresponding elements pairwise until a nonzero result is found; imposes "dictionary order." If the end of one iterable is reached, but not the other, the shorter iterable is considered to be less than the longer one. For example, a lexicographical natural ordering over integers considers [] < [1] < [1, 1] < [1, 2] < [2].

        Note that Collections.reverseOrder(lexicographical(comparator)) is not equivalent to lexicographical(Collections.reverseOrder(comparator)) (consider how each would order [1] and [1, 1]).

      • isInOrder

        public static <T> boolean isInOrder​(Iterable<? extends T> iterable,
                                    Comparator<T> comparator)
        Returns true if each element in iterable after the first is greater than or equal to the element that preceded it, according to the specified comparator. Note that this is always true when the iterable has fewer than two elements.

      • isInStrictOrder

        public static <T> boolean isInStrictOrder​(Iterable<? extends T> iterable,
                                          Comparator<T> comparator)
        Returns true if each element in iterable after the first is strictly greater than the element that preceded it, according to the specified comparator. Note that this is always true when the iterable has fewer than two elements.

      • min

        @Beta
public static <T extends Comparable<? super T>> T min​(T a,
                                                      T b)
        Returns the minimum of the two values. If the values compare as 0, the first is returned.

        The recommended solution for finding the minimum of some values depends on the type of your data and the number of elements you have. Read more in the Guava User Guide article on Comparators.

        Parameters:
        a - first value to compare, returned if less than or equal to b.
        b - second value to compare.
        Throws:
        ClassCastException - if the parameters are not mutually comparable.
        Since:
        30.0

      • min

        @Beta
public static <T> T min​(@NullableDecl
                        T a,
                        @NullableDecl
                        T b,
                        Comparator<T> comparator)
        Returns the minimum of the two values, according to the given comparator. If the values compare as equal, the first is returned.

        The recommended solution for finding the minimum of some values depends on the type of your data and the number of elements you have. Read more in the Guava User Guide article on Comparators.

        Parameters:
        a - first value to compare, returned if less than or equal to b
        b - second value to compare.
        Throws:
        ClassCastException - if the parameters are not mutually comparable using the given comparator.
        Since:
        30.0

      • max

        @Beta
public static <T extends Comparable<? super T>> T max​(T a,
                                                      T b)
        Returns the maximum of the two values. If the values compare as 0, the first is returned.

        The recommended solution for finding the maximum of some values depends on the type of your data and the number of elements you have. Read more in the Guava User Guide article on Comparators.

        Parameters:
        a - first value to compare, returned if greater than or equal to b.
        b - second value to compare.
        Throws:
        ClassCastException - if the parameters are not mutually comparable.
        Since:
        30.0

      • max

        @Beta
public static <T> T max​(@NullableDecl
                        T a,
                        @NullableDecl
                        T b,
                        Comparator<T> comparator)
        Returns the maximum of the two values, according to the given comparator. If the values compare as equal, the first is returned.

        The recommended solution for finding the maximum of some values depends on the type of your data and the number of elements you have. Read more in the Guava User Guide article on Comparators.

        Parameters:
        a - first value to compare, returned if greater than or equal to b.
        b - second value to compare.
        Throws:
        ClassCastException - if the parameters are not mutually comparable using the given comparator.
        Since:
        30.0