Package org.apache.commons.collections4.comparators

Class ComparableComparator<E extends Comparable<? super E>>

java.lang.Object
org.apache.commons.collections4.comparators.ComparableComparator<E>
Type Parameters:
E - the type of objects compared by this comparator
All Implemented Interfaces:
Serializable, Comparator<E>
public class ComparableComparator<E extends Comparable<? super E>> extends Object implements Comparator<E>, Serializable
A Comparator that compares Comparable objects.

This Comparator is useful, for example, for enforcing the natural order in custom implementations of SortedSet and SortedMap.

Note: In the 2.0 and 2.1 releases of Commons Collections, this class would throw a ClassCastException if either of the arguments to compare(Comparable, Comparable) compare} were null, not Comparable, or for which compareTo gave inconsistent results. This is no longer the case. See compare(Comparable, Comparable) compare} for details.

Since:
2.0
See Also:

  • Field Details

  • Constructor Details

  • Method Details

    • comparableComparator

      public static <E extends Comparable<? super E>> ComparableComparator<E> comparableComparator()
      Gets the singleton instance of a ComparableComparator.

      Developers are encouraged to use the comparator returned from this method instead of constructing a new instance to reduce allocation and GC overhead when multiple comparable comparators may be used in the same VM.

      Type Parameters:
      E - the element type
      Returns:
      the singleton ComparableComparator
      Since:
      4.0

    • compare

      public int compare(E obj1, E obj2)
      Compare the two Comparable arguments. This method is equivalent to: 
      ((Comparable)obj1).compareTo(obj2)
      Specified by:
      compare in interface Comparator<E extends Comparable<? super E>>
      Parameters:
      obj1 - the first object to compare
      obj2 - the second object to compare
      Returns:
      negative if obj1 is less, positive if greater, zero if equal
      Throws:
      NullPointerException - if obj1 is null, or when ((Comparable)obj1).compareTo(obj2) does
      ClassCastException - if obj1 is not a Comparable, or when ((Comparable)obj1).compareTo(obj2) does

    • equals

      public boolean equals(Object object)
      Returns true iff that Object is a Comparator whose ordering is known to be equivalent to mine.

      This implementation returns true iff <i>object</i>.{@link Object#getClass() getClass()} equals this.getClass(). Subclasses may want to override this behavior to remain consistent with the Comparator.equals(Object) contract.

      Specified by:
      equals in interface Comparator<E extends Comparable<? super E>>
      Overrides:
      equals in class Object
      Parameters:
      object - the object to compare with
      Returns:
      true if equal
      Since:
      3.0

    • hashCode

      public int hashCode()
      Implement a hash code for this comparator that is consistent with equals.
      Overrides:
      hashCode in class Object
      Returns:
      a hash code for this comparator.
      Since:
      3.0